First we need to create a Custom Field, so the module can look up the correct salutation for the client.
1. Navigate to Setup → Custom Client Fields
2. Create a new Dropdown Field. Choose the fields name and values as you wish. The result should look like on this screenshot:
3. The options Required Field and Show on Order Form are optional. If you do not want to let the clients select their gender, then do not check that options.
That could make sense if your clients are mostly males or womens.