How to invite friends to Red Dead Online
Once you've loaded into a Red Dead Online, press left on the D-Pad to open the Free Roam menu. From there, choose the "Players" option. This will show you all the players currently in your lobby, and you can invite any of them from this menu. To join friends or your crew, use L1 / R1 or LB / RB to browse the different categories. To invite someone, select their name and choose "Invite to a session". They will receive an in-game notification that they have been invited to your lobby and can accept the Invites section of their free roaming menu if they wish.
To invite friends to Red Dead Online on PC, open the free roaming menu with the L key, select 'Players', and use Q and E to switch between Nearby, Friends, and Crew.
How to form a posse
Of course, if you want to tackle any of the free roaming activities, PvP modes, or story missions in the game, you're going to want to stop. Starting a group is incredibly easy. Simply open the Free Roam menu, select "Posse", then form a temporary group or a persistent group.
A temporary detachment is basically a group or team that will disband when everyone else leaves. It's the same as grouping together in any other multiplayer game. A persistent group is permanent. You and your friends can make your mark at the border with your own officially recognized group, with your own name and side. This is similar to a clan in other multiplayer games. If you have a group of friends who regularly play Red Dead Online, the persistent group will be worth it in the long run.