I can use potions before battle, but is there any way to use those potions while in battle? I've heard about "heal" magic, but does it require weapons or armor imbued with "heal" spells? When can I use those "heal" spells? What are my options?
You can only heal in battle with the Heal spell as potions are only usable outside of battle. You can use the heal spell as you would any other spell. As you can't use magic outside of battle, you can only heal outside of battle with potions.
This handy list lists all the rings and their effects. Rings with the heal spell listed there are: