[MikeBmusic]

First, set up in a room at home (plug both mic and guitar in) and start messing around with the controls to hear what each one does. Ideally, get a friend in who can tell you what sounds best after you've adjusted things.

You probably need to do a lot of reading, it sounds like you're lost about things like tone/EQ.
Low - bass frequencies (small Hz number - Hz is frequency, cycles per second)
Mid - frequencies where most of the guitar and vocal tones are (200-1000 Hz)
Hi - treble frequencies, where the higher notes and sound is, this is the range that allows sound to cut through other noises and give some 'air' (>1000Hz)

Start with all the tone controls in the center position on the amp. Listen to the sound of yoru guitar when played thorugh it - does it sound balanced, or too much bass, or too shrill? Adjust the tone controls to change the sound.
Same thing with your vocal mic. Then with both together, how does it balance? This is where having someone else listen and comment will help.

the Loudbox has an XLR "Mix/DI" output jack on the back panel - this is where a cable would be plugged in to run to a PA system. It also has separate channel 1 and channel 2 DI outs if you wanted to send the mic and the guitar to separate PA channels.