[modeller_usage] missing sc atoms and rotamers

Dear all, I'm new to modeller and I hope you can help me to solve this simple problem.

I have 2 pdb structures of the same protein but with two different ligands. The first pdb is complete while in the second structure some sidechainsatoms are missing. What I need is to simply complete the missing sidechains in the second pdbon the basis of the rotamers they have in the first structure.

Please, excuse me if this subject has been already addressed elsewhere

Thank you Micheal