How to alchemize
To alchemize, all you ned to do is go to the alchemist, I believe it's the 2nd button, unless you have quests, then it's probably the 3rd.
You gain ingredients through breaking all the unneeded equipment, alchemy stuff is usually the way to get good equipment until after 40.
How to enchant
The number of elemental stones you need depend on level of the weapon. Armor enchanting is rather low in comparison towards the weapon,
If the weapon is level 40, you'd need 20 stones.
2nd enchantment would be the original cost(which is 20 in this example)*3+3.
I'll explain enchantments here:
What does each element do
Go here, Enchantments