[Koha] Unable to enter Data in 100$a

Sir/Madam Currently I am using Koha 18.05 in Ubuntu 16.04. I have imported data and successfully running. Now, I got new books for that I have to enter data. But field no 100$a is locked, it went to authority. How to solve this problem? Kindly Guide me. Rajesh Bhatt GRIMS, MBA College, VAPI India +919824925609 (whatsapp)