Make sure to put your items on your inventory. (Not treasury or exchange market)
Login your account at accounts.rohan.ph and click Special Candy Powder sub menu located on the top menu.
Select the weapon or armor you want to upgrade and click the "1 (5K points)" button. Click the yes from the confirmation to continue the upgrading process.
Make sure to logout first your character before upgrading your item.
You can only upgrade your item/s once
As of now upgraded items using candy points are bug in exchange market and don't put your upgraded item/s on exchange market