The ground wire from the battery is bolted to the bottom front part of the starter.
A ground wire is always connected to the negative post of the battery, which is the reason it is called a ground and is black in color.
In some cases you can connect it to the engine near the starter if the wire is short. The starter draws the most power so it is usually connected as close to the starter or on the starter if you can reach it. Be sure the connection is clean and getting a good connection.