Turn off power at the breaker
Verify power is off with a voltage tester
Identify the line, load, and traveler wires
Connect the hot line 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 between the traveler terminals on both switches
Connect the ground wires to the green grounding screws on both switches
Connect neutral wires together in the box if present and required
Secure all wire connections with approved wire connectors
Mount the switches into the electrical boxes
Install the cover plates
Restore power at the breaker
Test the switches from both locations