Solder the pins for the new micro switch to the board.

Get your iron up to temp. 400C degrees.

Tin your iron by placing a small amount of solder on the tip of the iron.

Heat up the joint by placing the tip of your iron against the intersection of base of the circuit pad, and pin [joint]. After 3-5 seconds it should be sufficiently heated.

Continue to hold the soldering iron on the pad, and pin and touch your solder to the joint.

A well made joint is smooth and shiny. A cone shape, like a volcano. Repeat process for other pins.