This step will require a soldering iron, solder with flux, solder vacuum and/or solder wick. I highly recommend learning soldering and de-soldering for through-hole components before attempting, this is not an easy first soldering experience.

Use soldering iron to heat the existing solder joints to flowing, and then apply wick or solder vacuum to remove solder. Once sufficient solder has been removed, the inoperable switch can be removed from the PCB. Take note of the orientation of the removed switch by viewing the raised lines on the bottom of the switch.

Insert new switch into PCB while matching of the orientation of the removed switch. The raised straight line(s) should be in the same direction as the removed switch's straight line(s).