How to connect a second line in my home

I have added a second line to my home for office use. I'm wondering if anyone could help me with instructions on how to change the wires on the jack in my office. I was not here when the telephone line was added, and they just recommended I switch the wires around to make a different line come into my office. This will be used as a fax machine and I need to get it hooked up.

anybody out there- thanks
Brett