Welcome to Wikitree and thanks for jumping in and asking a question.
1. Each of the G2G Categories are defined underneath the drop down. You chose well enough for this question. It could be under Tech since you want to know how to use the site to find surnames, Tree house is sort of a Misc. or all other type questions and it could go there as well.
2. You can find your surnames under the My Wikitree box at the top of your profile page. Click on it and scroll down to Surnames.
Also, you might check out your Watchlist, (also found under My Wikitree) these will be all the profiles you are managing. Your Watchlist can also be found under Find at the top of your profile, Family Watchlist.