This is a guide that someone on Reddit wrote and it helped me a lot. It looks complicated with the first glance, but when you do the steps it takes less than 15 minutes. I changed the order of the original slightly and added a few infos to make it easier:
“Guide installing Stremio with Torrentio and Real Debird on your desktop.
Stremio
Go to www.stremio.comDownload the relevant client for your platform (Windows/Mac/Linux) Open Stremio and sign up with email or facebook
Real Debird
Go to real-debrid.comSign up Go to Premium Offers ($3 for one month, $16 for 6 months) Choose a package and subscribe
Torrentio
Go to torrentio.strem.fun/configureChoose your options for providers, quality, foreign language etc You can now choose to install Torrentio without a Debid Provider. Personally I use Real Debrid to connect directly to a server vs having my IP shared in peer to peer and to speed up performance. Torrentio has a slot for a possible API key (the Real Debrid key) To install with Real Debrid follow the next steps: Go to the API key with this link: real-debrid.com/apitokenCopy the API Key and go back to Torrentio and paste it under RealDebird API Key Install
Stremio with Torrentio installed
Check the addon installed correctly Click the puzzle piece up on the top right that says ‘Show All Addons’ Click My Addons and scroll until you see Torrentio Test stream a movie or TV show Go to Discover Click on a Movie or TV show and click ‘Show’ You should now see [RB+] Torrentio - Quality Enjoy streaming”