Best thing to do I guess, is to take out the ashtray and loosen the cable.
Then pop the wheels off, one at the time if you prefer, and rotate the disc until the rubber cover is at 12 o clock position, remove said cover and adjust the brake adjuster wheel with a flat blade screwdriver until the disc doesn't rotate anymore, back off a few notches and replace rubber cover and replace wheel, repeat on the other side.
once everything is back on, adjust the cable inside behind ashtray to your liking and jobs a good 'un.
(Should I have omitted anything, I'm sure Alex or somebody will point it out)
Hope this helps