Models available

Are there models available in JME, i.e. trees, how will i put them on the terrain?

You can import models from 3D Studio, Collada, etc. and use them in jME.

Anychance u would be able to give me an idea of how to add models onto my terrain?

thanks

Have you looked into MonkeyWorld3D?  Search the forum for that if you're interested.