You will need to have any Item that you want to upgrade
And a Jewel of Bless or Jewel of Soul
To "USE" the Jewel, you need to click on it to pick it up, and then while you have it picked up, you need to click again on the item that you want to upgrade!
However there are requirements to do this!
Here's an example:
You have 2 Jewels of Bless and a Dragon Armor +5
All you need to do is pick up and place the Jewel of Bless on the Dragon Armor and it will LvUp to +6.. now you want to make the Dragon Armor+7, You try to place the Jewel of Bless on it, but it doesn't work!
The reason why it hasn't worked is because the Jewel of Bless can only upgrade items up to +6, you will need to Jewel of Soul to continue upgrading it!!
Jewel of Soul can upgrade your items up to +9
However you can also use Jewel of Soul on a +0, +1, +2, +3, +4, +5 instead of the Jewel of Bless.. It is highly recommended that you only attempt this if your item have "Luck"
Jewel of Life is also used to upgrade your items, however it adds "extra" Defence=Armors,, Attack=Weapons to your items by 4 (shield by 5)
Plus, Jewel of Life will never fail, even if the item doesn't have LUCK