I don't really think joining any groups would actually get you better at the game itself (Besides getting pp maps or mental advices i guess). The best you could do is configure your settings, grab a skin you like and figure what the game mode (osu!standard in this case) has to offer.
it's just like what you do when starting out any modes, play a few easy maps until you get the hang of the controls. No need to stress about improvements at this stage! (As there really isn't any gimmicks when you are just starting out...)
It's not a fast process though, so bless you!