Used psr 600

I just bought a used gre psr 600, it's programmed for the Nova Scotia Tmr system and a lot of air and fire departments but not from my region. How do I delete the frequencies I don't want and add the new ones I want? Do I need a certain software to hook up to my windows computer? I want to keep the Tmr systemtthat's programed in it, just delete the stuff I don't listen to and add around 30 vhf frequencies and eventually the new Tmr 2 system. Thanks for the help!