I've bought clips similar to this but they slide up and down really easily - so I'd have put my bra on with the clip in front, turn it around and the put the straps over my shoulrders.

The nice thing about this one is that it stays in place really well, so I can just slip my bra on over my head and then clip it together (the bra's normal clips) in back. This can make your bra can be racerback and thus be much more comfortable. It won't really give you more cleavage as it'll put the bra cups at an slightly awkward angle at which it's not meant to support your boobs but at least it's more comfortable.