The vet gave me Vetropolycin to put on my cats eye?

That's a very effective ointment for most minor eye issues. One thing you can do is put a strip of it on your finger tip, and use your finger to put the ointment in his eye (you may need your other hand to hold his eye open). This way you don't have to worry about poking him in the eye with the metal tip of the tube. You need to use a pretty good size strip though, not a tiny one.