Blocking sleeve cap seam

Hello - this is my first post! I have just sewn the sleeves into my first sweater with sleeves and the sleeve caps are all bumpy. Can I steam them in place and take out the fullness that way? I blocked the pieces already. The yarn is alpaca. To steam the caps in place, could I roll up a terrycloth towel and put it in place and then steam or spritz it? I have a steamer. Do I do this on the wrong side or the right side?

Thanks,
Eileen