Tighten the two screws into the box keeping it as plumb as can be. To convert a 3 way switch to single pole one of the traveler wires is removed from the switch.
How To Wire Switches
Changing a 3 way switch to a single pole switch. A single pole has 2 terminals the line can go on either one but normally you put the line on the bottom screw the other to the light on the top screw top of switch shows on when switch is up. To use a three way switch as a single pole one connect the hot wires to the common terminal and the traveler on the same side of the switch body. Now press the switch into the box for a test fit. You may have to adjust the wires in the box to make everything fit. Dominick amorosso decemberj2012 110 volt electrical 11 comments 24225 views in this video i explain just how easy it is to add a three way switch to an existing single pole one switch lighting circuit. It will not work if the wires are connected to the two traveler terminals.
Replace the switch cover and tighten its two screws. You would use one of the dark colored screws with one of the light colored screws. You dont need the other terminal on the three way switch so its fine to cover it over with electrical tape to ensure the terminals dont get mixed up. How to wire a three way switch to a existing single pole light switch circuit. In order for a 3 way switch to function as a single pole the wires need to be connected to the common and one of the traveler terminals. Watch the wires in the box as you tighten the switch screws as not to damage the wires.
You can wire a 3 way switch as a sigle pole switch by finding which screw terminals work together.