How do I refill supplies?

Im kinda new to the bot and was wondering how do you refill supplies? I have already seen the guide, but I didnt quite understand how it is done.
Please help me!

First..

Slect the Suplies section
Create your supply list...
Example;

Item; Mana Potion
Leave at; 20
Rule; up to 300 units
Category; a


Then... create your waypoint... go to the NPC... create an action with this.... resupply('a')


xD