Easiest would be to click on the 'A' button, select 'generate' and select 'symmetry mates'. From there you can select within how many Angstroms you want your symm molecules to be displayed. From the symmetry related molecules that get displayed you can select the one that completes the dimer.
Alternately you could try the following command:
symexp sym=pdb,(pdb),4.0 # Creates symmetry partners within 4 A of molecule pdb
Hope this helps.
From: email@example.com on behalf of Lisa M Jones
Sent: Thu 3/22/2007 5:57 PM
Subject: [PyMOL] dimer
I am trying to open a crystal structure of a dimer but I can only get
the monomer to open. The pdb file has the symmetry coordinates but I
don't know how to turn them on. Can anyone help me?