Place the wick on the joint or track you want to clean up, and apply your soldering iron on top. When it heats up it also melts the solder which is drawn out of the joint. If there is a lot of solder, the wick will fill up, so gently pull the wick through the joint and your solder gun, and the solder will flow into it as it passes. You need to get one if you do lots of repair work especially deals with the SMD IC’s