To compete in warzones you click on your faction icon in the bottom right corner of your minimap and join a queue. There is one queue for level 10 - 49 characters and all your stats are buffed to what they would be at 49. The second queue is for level 50 characters only. There are also ranked warzones for full groups of 8 level 50 characters. Basically you only need to be level 10 to take part. If you are unsure what to do in a warzone, please ask. There are guides including in the PvP section of these forums but sometimes things may not be clear, so ask. The first time you load into a Huttball warzone you will get a new ability "Pass Huttball" take a second and keybind it.
Do I need to be part of a guild?