Put the item you want ot Enchant together with a Lv 1 Puzze bit with the stat you want to give your equipment.
It should be looking something like this:

Hopefully it will work and tadah~! Your equipment is now enchanted.

If you want to remove the enchanted stats you ave to go to the same NPC and buy a cube for the stat you want to remove. The cubes will cost a couple of thousand Latale Ely, but Im sure you can afford it. (A level 1 cube costs 1000 Latale Ely, while a level 7 cube will cost about 27000 Latale Ely.)

It pretty much works like a enchanting.
Click the enchant item button, put in the equipment you want to down grade, put in the cube and press Execute. Tadah~! Your weapon is now downgraded!
A small warning, When you Enchant or Downgrade your weapon it maybe will get destroyd. However, It depends on the success rate. Hopefully you're lucky.

NOTE: A equipment can only be enchanted to a special level. The lower the level, the less will you be able to enchant it and reverse with higher leveled equipment.

Be sure that you've checked all the marked fields.

Good luck!

Pie's Quest Guide - I had totally forgot which level you needed to be when doing the mining Quest.
Thankfully, this guide saved me. Be sure to check it out and while you're at it, Please read all the other guides.

Thank you for taking your time to read this and hopefully you've learned something.
I'm so sorry if this guide is bad. So sorry!
Anyway, If you find any errors, like spelling errors or a information mistake. I'd be glad if you told me that so I can fix it.
I'm sorry for making your eyes bleed for all the text.
Thanks again for reading this guide.
Once again I hope you learned something.
Now I'm gonna go back and mine.