How to decrease in ribbing?

[daesania]

I'm making this pattern: http://www.ravelry.com/patterns/libr...n-up-baby-wrap however I like the look of the ribbed one, which is slightly different from the original pattern, but its just a 2x2 ribbing.

Now... what do I do when it comes to the decreases? I've never decreased with ribbing without a pattern. Do I keep the knits in the same spot and P2tog to keep that ribbing intact?

Sorry if this is a newb question, i'm clueless without patterns!!