How to add a skill card to a weapon?

and Konnichiwa! Naomi desu aka ShizukaOrizaki is my ign.

Hit the Alt button then on the top left hit "My Character" then to "Inventory"
Once there, look on top under "Other" click on the 4th tab then choose one of the following.

Be wary that certain skills only work on a specific type of weapon and you must equip the weapon that you want it's skill to be changed to.

When you click on the skill you'd like to use, there will show which weapons you have equipped that are eligible to have a skill changed. If you don't have an empty spot, it'll change one of your available weapons into that new skill.

Side tips : Dont use Ougi at low level. At least, 45+ above, so you not going to change weapon everytime. Find decent damage and put Ougi. Its much better if Ougi have same element as Weapon for extra damage