Attributes can be added by following the below process.   

• Login to Identity Bridge.   
• Go to Configuration Hub.   
• Go to Configure Source.   
• On the Active Directory Management tile click on the edit button.   
• Click on the Attribute tab.   
• Click on the ‘Add Fields’ Button. Perform this action if you want to add Custom Attribute Mapping. Be sure this Attribute is present in Target System. 
• Enter the Field Name, Field Description, Field Type, Pattern, Field Size.   
• Enter Scim Name as “Custom.Given Field Name”.   
• Click on Search Icon on the right side of the page, to search an attribute.