If it's a fondant cake, you can put satin ribbon around it by just wrapping it around and taping it at the back in a way that the tape doesn't show, easy as that.
Fondant itself can be made into the ribbon by cutting it into strips, but you have to make SURE they're even, and then you need to moisten the back of the strip and wrap it around same as above, and it just sticks to the cake.
Not sure about on BC cakes--I've never done ribbon on those, but I would wonder about the butter issue and grease versus satin, grease stains, etc.
Did you make sure that the dye used on your ribbon is FDA approved ? and also your wax paper, make sure that the wax on it is FDA approved ...
and everything else that touches your cake !!!
I'm just kidding !! 
Maybe cut the ends exactly where they meet, to avoid overlapping, then use any icing to stick them. Show us a photo of your cake when it's done.
I'm sure it's beautiful. Have a nice day... 
If you're putting ribbon around buttercream, the best advice I can give is to make sure your buttercream is fully crusted before attempting to do this. I learned this from experience.
I would recommend that you let the icing crust overnight if possible before putting the ribbon on.
Did you make sure that the dye used on your ribbon is FDA approved ? and also your wax paper, make sure that the wax on it is FDA approved ...
and everything else that touches your cake !!!
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