I do 100% pvp, last night I lost a node to the Imps, And someone on my team started bit chen saying I did not even have my cylinder activaded, I looked and looked can't anything that says a cylinder in my tree. I'm level 30 with the assault build. If anyone can help me out.

You need to run the Plasma Cell if you are running Assault.

your spec determines what cell you should be using. i think cylinder is the bounty hunter terminology. if you are assault you use plasma cell. if you are tank spec you would use ion cell. and if you are tactics, then use high energy cell

 

the talents in your spec will add bonuses to what each cell does, like higher crit or damage, or chance to proc some other stuff

 

generally you are not going to be switching from one cell to another unless you have some kinda weird hybrid build. i'm assault so i always and only use plasma cell.

 

the cell you are using shows up as a buff on your bar so if you don't see it, go to your skills tab and make sure it's active. your cell persists through death so you really never have to worry about it unless somehow you right-clicked your buff to disable the cell

Thanks Guys I will check when I get home from work