Ok i bought several spawn eggs today, i am very new to minecraft and love it. i tried using 3 eggs in my house i right clicked the egg by itself it made the animal and the vanished from my inventory. i tried it again to see if maybe i did something wrong, with the same results. i contacted a mod and an admin and maybe it  was hard to understand what i was saying i thing a hacker had just been caught or something ,but they couldnt help me. i did gather from the admin that i couldnt use it in town so i walked out till it said i was in the wilderness and also put it in a dispenser , it made 1 animal then no more i looked in the dispenser and the egg was gone again. So it is a very good chance this is a lack of knowledge on my part thing so if anyone can tell me what went wrong i will be thankfull.

You'd need to use it on a  monster spawner if you were wanting to make more than one mob. And that only works with passive mobs (Excluding squids), not hostile ones. Some people make the mistake to think it'll work with hostiles.