So just need to modify with other armours at workbench, yeah?
No, repairing any item is done completely in your Pip-Boy inventory screen. When you have an item highlighted in your Pip-Boy, there is a list of actions you can perform with that item in the top right corner of the screen. One of the actions listed is Repair.
So, highlight your armor, push whatever button is listed next to Repair, and you'll get a list of items that you can use to make the repairs. When you select an item from the list, it will be used to make the repairs and disappear from your inventory.
If the Repair option is grayed out, that means you don't have any items that can be used to repair whatever item you are highlighting.