How to be a Dom?

The guy I'm seeing has told me multiple times that he wants me to dominate him but I have no idea how to go about it. I'm a very submissive person sexually so this is very unfamiliar territory for me. I did try once, and it was a fiasco. I blindfolded him and went down on him, teasing him along the way, but then I tried to get on top and was just giggling uncontrollably. I tried to pin him down, but I'm tiny so that didn't work. I tried to tickle him with a feather duster but that just made me giggle too. What the heck am I supposed to do?