Changing PA30 fields from Display mode to Change mode

Hi Friends,

Can you Please provide me a solution for the Below Problem:

When I go to PA30 and try to CHANGE infotype 0001(Org Assmt),I get the fields "cost center,Position,job,org unit" in the Display mode I am not able to change those fields.

Where can i change(In the configuration) these fields to be changed from DISPLAY MODE TO CHANGE MODE.So that in PA30 I can change these fields in IT0001

Thanks In advance

Gopi Palleti