I just got Minecraft Pocket Edition on my iPhone, but I'm having trouble figuring out how to start multiplayer. When I go to menu, there is only one button that says Play. How do I join or create servers?
If you have the free version you will not be able to join or create multiplayer games. If you have the premium version you have to press the button down in the corner to the right, this will take you to a menu that will say 'Local server multiplayer' it is a on/off switch, set it so that the switch gets lighter.This enables other people on the same Wi Fi network as you join your game. This works for me on the newest version of premium Minecraft PE, so it should work. The only thing is you can't yet play on multiplayer if you are not on the same WiFi connection.
If you want to play with lots of people that aren't on the same WiFi network, get the Multiplayer PE app and it will give you instructions. Although, in my experience, there are many bugs with this app, and most people who play are greifers.