The Astral FAQ and Permanent Astral Topics are loaded with various techniques and experiences for AP. If you are just starting out, I would definately read through them and try some of the stuff.
As to how to "add stuff" in the astral -- its all mental. Not so much mind over matter, but will power. You very clearly imagine what you want to make -- as clear as possible. And it will appear before you. The astral is extremely susceptible to thought and feelings. So what you focus on, happens/appears. Not just what you want to happen, but also what you don't want to happen.
Fear is a big hang up for people starting out. The more focus/thought they put in to what they fear they may experience only increases the chances of that happening. So a good rule of them is while you are practicing techniques, also practice maintaining awareness and focus during the day. Minimizing your mind from wandering and lingering on negative thoughts will only help you when you finally 'get out'.
ahh i gotta get here
when i wasnt a member here i remember reading about this one guys astral island he got set somewhere in feudal japan and he's a ninja there
when i get there i'm gonna challenge him to a battle then we'll be friends
yeah