Add the custom control to a Nintex form
Open the Nintex Forms designer in the list, drag the custom control to the form surface, and then bind to a list column.
To verify that the custom control displays in the form designer
- In SharePoint, navigate to the list to which you would like to add the Nintex Form with the custom control.
 - Click LIST in the SharePoint ribbon, and then click Nintex Forms to open the Nintex Forms designer.
 - Find the control in the list of controls under the New Controls group.
 - Click and drag the custom control to the form surface to add the custom control.
 - Double-click the custom control to open the Control Settings window.
 - Select the list column to which you would like to bind the control from the Connected to list. You will need to bind the control to a number column type in SharePoint or you will receive a configuration error when you preview the form or attempt to view the form.
 - Click Save.