[Koha] We need your help

Hello all, we are using koha 3.8. when we add new records to koha, the personal name text box is not enabled in 100a tag. is there a way to enable or how do we add personal author name. The same problem for adding series statement i.e 440a, Subject add enty personal name 600a, & add entry for personal name 700a, Dagne Woldie ICS library Addis Ababa