Please follow the steps mentioned below to create Custom Field.

1. Go to Admin options.
2. Click on Custom Fields.
3. Click on Manage Link of the appropriate Page in which the Custom Field is to be created.
4. Select the Data Type of the Custom Field from the Drop down.
5. Fill in Required Fields and click on Add.(Note: Enable/check the “Is Required” field if you want the Custom Field to appear as the Mandatory Field)