To start using a Custom Button you created, admins will need to add it to a Page Layout. Up to 6 buttons can be added to a layout, including standard and custom objects.
To add a Custom Button to a Page Layout:
- Go to System Settings > Objects and Fields. Select an object.
- Go to Page Layouts and select a layout.
- Under Available Buttons, click and drag your button to the Custom Buttons section of the layout.
- Click Save Layout.