How do I change the essential field settings on Jobs & Experts "Add New Expert" form?

Hi,

See http://twid.simplecsr.com/demo/

THE BIOGRAPHY FIELD -

When adding a new Expert the biography field is an essential field. If less than 200 characters are entered it says "The Biography field needs to be longer than 200 characters."

How can I change this field?

1. I would like to remove the character limit. (or reduce it to a very low amount e.g 10 character)

2. I would like to make it a non essential field.

Thanks
Chris