Use a tool like 7-Zip to extract the downloaded save files.
%LocalAppData%\Packages\Microsoft.254428597CFE2_8wekyb3d8bbwe\SystemAppData\wgs
Paste the new files into the directories listed above.
If you can't find it, look for a file named steam_emu.ini in the game's installation folder; it often lists the "AccountId," which helps you find the right subfolder in Public Documents . How to Install a 100% Save Game
Always copy your existing remote or wgs folder to a safe place first.
Launch the game, and your campaign progress should now reflect the new save. Common Saving Issues & Fixes