I want to draw a sample tree and a sample car with using opengl primitives like glWireCube,glWireSphere etc... do you have any suggestions for me?

All you will need will be glTranslate(), perhaps glRotate(), and the functions that draw the primitives. You'll need to know at least a little about how glTranslate() and glRotate() work, and how to use them to position things where you want them. The Red Book is a good reference for an introduction to coordinate systems and how OpenGL handles them.