With the script file://rose.bmc.uu.se/pub/gerard/omac/getpdb . It takes one argument, namely the PDB ID of a structure you want to look at with O. You can execute it from within O, e.g.:
O > $ getpdb 1guh
It does the following:
Outside Uppsala: the directory where you keep your local set of PDB files needs to be edited inside the script. Also, it assumes that you use the filename extension ".pdb" for your PDB files.