Under "Stable Releases", you want the most recent version of 3.9, currently version 3.9.9. You want the "Windows installer", either 32-bit or 64-bit depending on your operating system. (If you don't know your operating system, then right click on "My Computer" or "This PC" on your desktop/file explorer, click "Properties", and it will tell you somewhere in there if your OS is 32 or 64 bit.)
Once you've downloaded the Windows installer, simply double click to run. Make sure to check the box in the install wizard which says "Add Python to PATH".
Next, go to the folder where you extracted btcrecover. Hold down shift and right click, and you should see something along the lines of "Open CMD prompt here" or "Open PowerShell window here" (I can't remember the exact wording, it's been a while since I used Windows). Once you click on that command you'll get a new box pop up which says something along the lines of "C:\Some Folder\btcrecover>".
In that box you want to enter this command and hit enter:
Which will install all the requirements for btcrecover to function. Once you've done that, you can then enter this command:
Which will test you've done everything correctly.