In order to do that, you need to visit Mixing Craftsman, Morald in Ricarten Town.
But before going there, make sure you know the formula you are going to use, because if you make a mistake, all sheltoms will be lost.
A list of the formulas can be found here.
( Step 1 ) ( Step 2 ) ( Step 3 ) ( Step 4 ) ( Step 5 )
Step 1 :
Your item must be clean in order to be able to proceed to a mixture!
Step 2 :
Put your item in the left side and the sheltoms on the right side. Make sure you have enough money, and ensure that you insert the correct formula to proceed with the mixture! Afterwards, click on the red + in the middle of the window to start the mixture.
Step 3 :
Wait for the mixing formula to be processed.
Step 4 :
A popup will appear shortly, confirming that the mixture was successfully completed.
If it says "Mix failed", it means that you have inserted the wrong formula of sheltoms combinations.
Step 5 :
Take a look at your item statistics and you will see the modification and the added properties in blue.
In this example, you may see the "Add HP" property was added, and the "Attack Power" and "Attack Rating" properties were increased. Plus, your item will have its own mix effect!