Refer to the picture the poster above me linked to. Here are the slots:
Left column, top to bottom:
Quiver: Holds arrows or bolts.
Neck: You can equip necklaces or neck armor here. (Iolo is wearing magic gorget in this pic)
Chest: Chest armor, obviously. You can also equip cloth shirts and such but there's no reason to
Right Hand: Usually used for shields because any weapon held here isn't used in combat, except for hawks and fire swords. Hawks will still be thrown and fire swords will maintain their lighting effect when held in these hands.
Right Column, top to bottom:
Head: Helmets or hoods are equipped here
Back: Reserved for backpacks or other containers normally
Waist: Used usually to hold side weapons
Left Hand: Primary weapon the character will use
Hands: Where gauntlets are equipped. If no gauntlets are equipped, you can equip a ring in this slot and in a slot opposite to it that appears on the other side of the paper doll.
Legs: Leg armor, cloth pants. Same as chest slot really but for legs.
Very Bottom:
Feet: Normal armor, just use whatever boots complete the set. Wearing swamp boots will make someone immune to being poisoned by touching a swamp tile