The reason I am creating this guide is because 90 percent of other games on steam you can invite friends in friends and chat place. Inviting to games is easy, but this game is little bit different. You need to invite in this certain place and I want people to know this information because it's a great game that I think more people should own.
Enjoy one of the greatest co-op experiences ever created. Thank you capcom for resident evil 5 and please if you can give your older games some love with a patch that the switch ps4 and xbox one got.
Step one is start the game in chapter select or continue.
Step two is in the menu with your guns and ammo before you start a level you are you are going to press shift + tab
If nothing is happening make sure you have steam overlay enable in the settings of steam. it will be in the In-Game section.
Step three is on left side where it says friends is the only place you can invite people press right click the person name and it will say invite to game. I am not sure why this is only game I know that does this. Enjoy your co-op experience.