How to auto populate field Pick List menu

How to auto populate field Pick List menu

Hello,
I imported records into existing field types and the "Lead Source" field is a Pick List field type.  There are about 20 different phrases, ie, lead sources in that field in the database I imported.  Is there a way to have Zoho auto populate the menu list with the unique values of the 20 lead sources.

I don't want to have to type all of them into the list.  See attached picture.  Thank you.