UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? trying to find the constraints for total board width

I use css normally, so can you help me with code to get the background colour as #efefef or like on this site of ours
http://www.everybody.co.nz/

I have managed to get our forums to size to 1024px see here http://www2.everybody.co.nz/forum/

TIA
Wendy