Hi,
First of all, I'm not sure if I get the question right

If you mean what I think, here it goes.
I'm no pro at Charon but I guess you change it in the "Scan Options". There is a "Hunt Google/Lycos for proxies" checkbox that I guess you can uncheck. Then there is a list where you can right-click and add URLs. I guess you have to check "Leech additional pages.." too.
Haven't tested this myself so I have no idea if it's the right way, but... Good luck.
If you mean the "test against site"-thing I guess you can just remove google and add you own.