You're not supposed to. Rivatuner isn't the most user-friendly software out there. It's very good, but you'll need to research to take advantage of it. I don't use it - I'm too lazy and I have a Quadro4 (waste of money).
The original Sofquadro is part of Rivatuner only it doesn't work on GF4. Nvstrap will not turn your geforce into quadro - it will show it as quadro but won't add any pro features. You stil need a sofquadro4 (that is not released for "business" reasons) and an unprotect script. If you were a max4 user you could just use a hacked maxtreme for (supposedly) improved performance.