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Select My Apps in the top menu
Scroll across and select Contact Forms
You arrive on the Manage Contact Forms page
Either
choose an existing Contact Form to add the mobile number field to
Press the cog button in the Tools column
Select Edit in the menu
or create a new Contact Form
Press the New Contact Form button
You arrive on a page where you can edit the contact form
Select the Add New Field button
In the New Field popup, select Text Telephone as the type of field
In the Name field, write Mobile Phone Number
Select an Owner Type - choose Organisation
Set Privacy as Organisation Leaders & Editors
Press Save
The popup closes and the field is now added to the contact form
Scroll to the bottom and press Save
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