Hi @Grainne 
Welcome to the forum!
It’s a bit overwhelming if you’re not used to forums but hopefully it will all make sense soon once you’ve had a play. As @JoCat says, the search function works well to find topics you’re interested in.
For getting to understand the technical side of the forum the Discobot Tutorials can be a handy starting point and for any things like linking or formating you want to experiment with The Sandbox is a great place to have a play.
Otherwise, just jump in on subjects that interest you and enjoy.