The WOD all by itself will put more muscle on your frame. Couple it with thoughtful and consistent diet choices and you'll be kicking sand in no time.
To Steve's point above, ME days help, but if you've been watching those are coming pretty frequently of late. Since 30-Dec 6 of 21 WODs have been ME type (counting Linda). Go back to 1-Dec and it's 11 of 43, back to 4-Nov and it's 16 of 63. Closer to 1 in 4 but still a pretty good ratio, and something that looks like it's being consciously pursued by the moderators.
When I switched from powerlifting to crossfitting last April I wasn't small. I was a 225# with ~15% BF. Just doing the WOD for a few months got my BF down in the 10-12% range at a constant body weight, didn't really notice anything visually though.
In Sept I started eating 20 block zone 5 days a week (sat/sun I still eat zone ratios but don't count my total blocks) and have seen some increase in muscle seperation, my deltoids have popped out, I have 4 pack abs, blah, blah, blah. Got on the scale the other night after the WOD and was shocked to see that I weigh 244. Not my goal at all, but my performances have been good and improving, so I'm not complaining.
Consider this a very long winded way of restating the CF mantra of WOD and diet, sorry for the rant.