It is a crap skimmer, I would second taking it back to the store. It's a complete waste of money. But if you insist on using it and there's no way to hang it off the back, then you will have to hang it off the side of the tank.
Unfortunately it looks like the Odyssea B28 is not designed to support a skimmer.
I also have used the SeaClone skimmer in the past and it is not worth the money.
It required constant tuning of the venturi and had very low tolerance for water level variations.