Auto Select/Fill an Entry the Look-Up Field

I've been playing around with the CRM Template and I created a Stateless Template to allow customers to sign up online.

I've run in to an issue of the forms being submitted and the lead owner field being empty.

I want to have the Look Up Field auto Populate with the "WEB" Username Load, Validate or Click... pretty much at any part.

(Screen Cap)

Any help would be appreciated.