Turn off power at the breaker
Verify power is off with a voltage tester
Remove the switch cover plate
Identify the common terminal on each 3-way switch
Connect the incoming hot wire to the common terminal on the first switch
Connect the switched leg to the common terminal on the second switch
Connect the two traveler wires between the traveler terminals on both switches
Connect the ground wire to the green ground screw on each switch
Connect the neutral wires together if present in the box
Secure all wire connections with wire nuts
Mount the switches back into the electrical boxes
Install the cover plates
Restore power at the breaker
Test the switches from both locations