Turn off the circuit breaker and verify power is off
Identify the line hot wire, load wire, and the two traveler wires
Connect the line hot wire to the common terminal on the first 3-way switch
Connect the load wire to the common terminal on the second 3-way switch
Connect the two traveler wires to the traveler terminals on both switches
Connect the ground wire to the green ground screw on each switch
Secure all wire connections with wire nuts or terminal screws
Mount the switches into the electrical boxes
Install the switch plates
Restore power and test both switches