[Koha] Problem with entering Personall Name

I am currently entering manually Biblio records using MARC 21 Format in Koha Live CD version 3.02.00.04 but I cannot type in anything in tag 100 subfield $a which suposed to be Personal name field since the text area is like "prohibited" from typing in. So we used subfield $b which accepts being typed in but it is for something else. Hence we are getting null information on Author when we query on author field in SQL reports. So how is Personal name entered using MARC 21 Cataloguing? Thanking you in anticipation. Raphael Chisanga Muonga