The Add Fields panel of the Create New Entity Schema wizard lets you add fields to the new entity. Every entity must have primary fields, which are the unique identifiers of the asset type that you would create. So, ensure that you define the primary fields for every entity that you create. Besides the primary fields, you can also create optional fields for the entity.
The fields that are added through the Create New Field dialog box are displayed in this Add Fields panel. You must check the option, Is primary field if you want the added fields to be the primary fields in the entity schema. Unchecking the option makes the added fields optional.