i just did this over the weekend, you can just use a centre punch as long as its long and thin enough to fit in otherwise take something the diameter or a paperclip and punch it in (must be hard not to bend or break) problem about the rivets that i had/have is in the instructions in one spot it says use the expanding, in the other it says use expanding included now i tossed all of them out and the ones that came with the RB dont fit and keep falling out. i think i might just plug everything up with blind ones i dont understand why they didnt use blind ones. so i am currently driving around with a few missing but they are more for cosmetics since everything is already on tight. btw go to realoem.com and look through there to get the part numbers for the rivets from BMW ill post them here but thats a great site for any part ever necessary

Expanding rivet 51111944537 $0.22
Blind rivet 51717002953 $0.50