Path: Settings > Configuration > Lead

Default broker lead assignment is only potentially needed if you have only one lead management account for your brokerage site but have agents with their own Agent Sites. If you wish to have any leads gathered on your brokerage site assigned only to the broker for this site, check this box. If you want leads gathered on your brokerage site to be potentially assigned to agents with their own Agent Sites, leave this box unchecked and choose Auto-Assignment for your web leads.

Leads coming to your site can be directed to the unassigned leads pool (if you want to manually assign leads to your agents), or can be automatically assigned using the Auto Assign Leads checkbox. 

Auto Assign distributes leads among your agents with a round-robin system. *Auto Assign will only distribute leads to agents whose profiles have been set to accept automatically assigned leads.