drummerboy1533 pointed out the room shape to you which I do have to agree. But if this is the room you are working with then I would start by placing the mix position (where you sit) 38% of the room length. Then place bass traps floor to ceiling in all corners of the room. You may want to hit also some of the wall to ceiling corners also. At this point place some thinner panels (2" should be fine) in all first reflection points of the room (see our FAQ on my sig to figure this out). DON'T FORGET THE CEILING.
Last and not least you want to put some 4" panels on the back wall to help with sound hitting the back wall and coming back on you.
Hope that helps a little.
Glenn