How do I activate/deactivate custom fields? Follow

To activate/deactivate custom fields, 

• Navigate to the Profile icon on the top right corner 
• Click on the Setup
• Under Customizations, select the module for which you want to update the custom fields. For eg. Contact Module

• Drag and drop the field to the Inactive Fields and the field will be marked as Inactive. 

• Drag and drop a field from Inactive fields to mark it as Active.