[Chimera-users] Unrecognized command: "source"

Hi, I've just downloaded your program and was trying to run some alignments between two peptides. However, whenever I type in the command "source", I keep seeing the following error message: unrecognized command: "source" Could you please help me? I am able to run all the other commands, I just don't know why "source" is not recognized. Thank you, Pam Wang