Depends on what kind of ocarina you have. The ones I received as gifts wouldn't work, because they are too limited in what you can play with them. If they have only five holes or less it's going to be difficult. Also, if the ocarina is small enough to fit in your palm, it's going to be very difficult to handle, since your fingers will be very big in relation to the holes, so playing notes that require half-holes is harder.

There's a simple test you can do to see if it works, though. Just get yourself a sheet that tells you which grips correlate to which notes on your ocarina and play them all in order.

There's five lines for placing notes that are always shown on sheets, if the ocarina can play the note placed on the line below those five lines up to the note placed on the line above the five lines you're good to play pretty much all melodies.