Installation the module does not take longer than 10 minutes.
  1. Extract the module archive which you downloaded from the client area.
  2. Upload the module to your WHMCS installation.
  3. Go to the WHMCS Admin backend, click on Setup → Addon Modules and activate the module.
  4. Click on Configure.
  5. Enter your license key, choose the newly created custom field at the dropdown, select Full Administrator at "Access Control", click on Save Changes.
  6. Now, some new dropdowns appears. Select at the dropdowns the correct option and click Save Changes again.
  7. If you want to let your clients choose the gender, create a new custom field: Custom Field Creation

It should look like on this screenshot:


Custom Fields: Follow this guide to setup the custom fields.