Need help replacing headlamp dimmer switch

My regular headlights went off a couple months back, but i didn't have the money to
replace the dimmer switch, and I only drive it for 20-30 minutes 3 days a week at night,
so I ran on my high beams, but those two are out now.  From what I've read it sounds
like the dimmer switch, I just don't know where it's located, I assume it's behind the
dash where the pull out switch is, but i don't know how to get behind that area, right
above the fuse box.