It should look a lot like the attached picture. To tighten the cable, loosen the rearmost locknut and turn the long hex nut counterclockwise, pulling the cable towards the front of the bike and the brake arm along with it. With the bike on its stand, check the movement of the lever and the brake function often and don't tighten the cable too much or the brakes will drag. Then run the front locknut rearward up against the bracket and tighten the rear locknut to hold the whole thing in place. These adjustments should be done AFTER you have cleaned the shoes and drums.
If you need help with removing the wheels, come on back to the forum.