Hello. I was planning to set up a game with a friend soon. I know how to play, however I’ve never used this browser app before. Is there a wiki with more information? If not, can you help me figure out both how to invite someone and how to set up specific rules?
I apologize if this thread is already answered in an FAQ I didn’t see.
And welcome to OGS. Hope you enjoy your stay. 
I can’t resist but to link this here
But also you mention app. If you mean the online go Android app you can challenge a particular user via the “custom game” button.
This is why I think
is the most important missing feature on OGS. It lowers the barrier to entry for new players to the game.
Even more than my pet peeves of no undo request on your move, and handicap off and analysis on (recent woo!) by default.
This is rapidly reaching the top of my to-do list.
Can you do it all in the frontend though?