go to your apps and select the phone app...
and even though theres a sense on off switch on the evo, sense really isn't off. basically you just dont have the bottom bar/widgets but its still running in the background.
this kind of defeats the purpose because its still running in the background and now you just lose some nice features.
i dont mind sense with 2.1, but with 2.2 i think i will root/rom stock 2.2. because froyo is a little more feature packed so sense is unnecessary.