Navigate to Leads (click on People and select Leads).
You will be brought to you a list of your leads organized by their name, intent (buying, selling, renting), the source (ie: Zillow, Facebook, Boomtown), and status.
To add a lead, click New Lead under Status or click the plus (+) sign on the upper righthand corner.
Fill out the information and click the checkmark. You've now created a new lead!