The only requirement for creating an appeal is that it have a name. In the context of importing constituents to an appeal, you need to have a value in the "Gen. Appeal Name" column/field. Note: When loading gift records, you can associate gifts with appeals with the "Gift Appeal Name" field.
Custom categories and attributes (different types of fields) can be added to an appeal in LGL; during import those custom fields will be available if you choose to display them and choose the appeal. Note: If you want to import to these custom fields, your import file can be imported only to that one appeal.