Maybe mix a bit of stinky wet food in with it at first? Check with your vet.

When I started Oscar and Cole on the Omega 3 oil, I would mix it in their usual wet food (Royal Canin kd). They wouldn't touch it. So I resorted to adding a bit of the Fancy Feast junk food - it worked! And now they eat it without anything added (except the Omega 3-6 oil).