how i can use my guitar like a bass?

yeah, you just record the guitar through a DI and pitch it down an octave; I use the cubase/nuendo built in pitch shifter for that, don't know which program you are running though; I know people on this forum like Behindert got some insane results out of it!
 
yeah, you just record the guitar through a DI and pitch it down an octave; I use the cubase/nuendo built in pitch shifter for that, don't know which program you are running though; I know people on this forum like Behindert got some insane results out of it!
bulb gets some amazing tones as well