Hi Nail,
Chimera is not a docking program.  However, if you mean you just want to move the ligand to the receptor by hand, here is some description of how to move things and to “freeze” certain models so that they don’t move with the mouse.  You have to put the ligand and receptor in two different input PDB files so that they are open as two separate models.

<http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/mouse.html>
<http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/mouse.html#activedef>

Still, moving with the mouse may not be easy. 

If you want to do computational ligand-receptor docking with restraints, you would need to find a different program (not Chimera).

If you want to learn Chimera better, you could try some of the tutorials:
<http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/frametut.html>

I hope this helps,
Elaine
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Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

P.S. I changed the Subject line of the message since you are asking about a different thing than before.  This is so that other people can easily see what the message is about.