Step 1: Don't get in a hurry. It's a sure way to screw things up.
Step 2: If you're not sure anout how do do something, ask questions here.
Step 3: Watch lots of guitar building videos on the Internet.
Step 4: Double check, triple check, and then check again before drilling any holes. Make sure the location is correct, the size is correct, and the depth is correct.
Not sure what more I can add without knowing your skill or experience level.