The Xbox app for Windows is required for this to work. It comes pre-installed on Windows 10/11 by default, but if you have uninstalled it, you can get it from the Microsoft Store or with the official installer.
To find the game files, open the Xbox app, find Dungeons in the "Installed games" list on the left, then click the button with the three dots and choose Manage. In the window that pops up, go to the FILES tab and it should show where it is installed under "Installation info".
If you have any problems with this step (or any of the steps), make sure to check the troubleshooting section below.
Once you know where the game is installed, go to that folder in File Explorer, and then to Minecraft Dungeons\Content\Dungeons\Content\Paks
Create a new folder here called ~mods (Yes, with a ~) and put your mods in this new folder.
If you're not able to move files from a different drive to the ~mods folder, try first moving them to the same drive as the game, and then moving them to the ~mods folder.
If it says you don't have permission to move files to the ~mods folder, make sure the game is closed before moving the files, and if the files already exist in the ~mods folder, try deleting those before moving the replacements.
If the Xbox app says the game is installed in WindowsApps or another folder you don't have access to, click your name in the top left corner of the app, then select Settings. Go to the General tab and change the options in the "Game install options" section to your preference. Once that's done, reinstall Dungeons through the Xbox app.
If the Xbox app doesn't show the path to the installation folder, click your name in the top left corner of the app, then select Settings. Go to the General tab and find the "Game install options" section. This section should have options for changing where Xbox app games are installed. If any of these options are missing, then your Xbox app must be out of date and you need to update it through the Microsoft Store.
If the options are there, configure them to your preference, uninstall Dungeons, and then reinstall it through the Xbox app.
If you updated the Xbox app, but the options are still not there, things get a bit more complicated, check the Legacy Guide below.
Legacy Guide - Do not use this unless everything above fails
Legacy Guide
Selecting an installation folder that players have access to is a recently added feature of the Xbox app that makes it possible to modify Microsoft Store/PC Game Pass games. The feature might still not be available for everyone, and so to mod Dungeons those that don't have the feature yet must first extract the game files to a new folder. Unfortunately, doing so is a bit complicated, so below is a set of steps to guide you through the process:
Prerequisites
Temporarily disable any antivirus software. Most will detect that an unknown script is being run and try to stop it. Windows Defender should be fine to leave enabled.
If you use Bitdefender, you need to uninstall it before continuing, as it breaks the script even when turned off.
Make sure you have at least 15 GBs of space free.
Make sure your game is up to date. To do this, press Win + R, enter ms-windows-store://DownloadsAndUpdates/ and press enter. Then, press "Get updates" in the top right corner of the window that opens.
Install Visual C++ Redist. Even if you think you have it installed, try the installer. You may have an older version that won't work.
Setup
Click the Windows icon in the bottom left corner and enter powershell then click "Run as Administrator"
Paste this command into PowerShell and press enter:
It might ask you about an "Execution Policy Change" - Just press A and then Enter. In some languages, the key you need to press might be different. It should be the one next to "Yes to all".
You will be asked to select a folder. Choose an empty folder where you want the game to be moved to. Do not choose a folder in Documents, Desktop, Program Files or One Drive, it will break things.
The game will open at one point. Do not close it when this happens. If you run into any issues, make sure to check the Legacy Guide troubleshooting section below.
A ~mods folder will appear. This is where you place your mods.
Launching the modded game is just like launching the regular game. You can do it from the start menu, Minecraft Launcher, Windows Store, Xbox app, and so on, just like you normally do. Do NOT try to launch it by running the .exe files in the game folder.
Legacy Guide troubleshooting
If you run into any issues while/after patching the game, some of these things might help you.
If the game didn't open at all while patching and the patching didn't work, try opening the game manually before running the patcher. Keep the game open until it either closes by itself or the patcher finishes.
If you get an error saying it can't verify your ownership of the game, you must have launched the game using the .exe file. Don't do that. Run the game from the start menu, Minecraft Launcher, Windows Store, or Xbox app. If you did, but still get this error, reinstall the regular game and log in at least once (open the game and select a character) before patching it.