I don't know that anyone can help you without knowing what kind of tree. Since you don't know, post a couple pictures (at least one of the whole tree and one close up of the leaves)--instructions for posting pictures here are in New to Helpful Gardener under Helpful Tips and Suggestions for New Members. Likely someone here will be able to ID it for you. In order to take care of it, you really need to know.
Please also include a bit more information about conditions the tree is in -- what has your weather been like (very hot? very dry or very rainy? etc), is it in full sun, do you water it, fertilize it, etc.
Welcome to the Forum! Hope we can help you out.