Digitech RP50 patch question

Hey... When I am going to enter in a patch into my Digitech RP 50, I understand how to enter the settings that they give, but do I start with a preset (0-40) that I can customize like a distortion? Example.. I wanted a metal solo patch and found one. How do I begin? Start with a distortion customizable setting? Please help.. Or, I found an Enter Sandman patch, what setting do I start with???

Hi. I have the RP250. Never loaded anyone else's patches, but I found the forums on the Digitech site to be helpful. They would have the answers you seek....

http://www.digitech.com/