No you don't, the enchanter does al the work for you, all you need to do is provide him with the item you want to place the enchantment on, a gem with a trapped soul, and the amount of money that the enchantment will cost you.
For instance:
You say you have a gem with the soul of a golden saint, that's perfect, because those are the ones that make constant effect enchantments possible. Well now, let's say you have an exquisite ring, or an exquisite shirt, first you select that in the proper slot after choosing "enchant" in the dialogue screen, then you click on the gem you want to use. When it's a gem with a golden saint, you'll have the change to toggle between "constant effect" and "cast when strikes", select "constant effect", then select the enchantment of your choice. Next you can work the bars of how powerful exactly the enchantment is going to be, which will explain itself while you're at it. When all is done, you'll see the amount of money it's going to cost you, pay the man, and you have a shiny new enchanted item, all done.
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