Leads
Any sales record (Quote, Booking, Invoice, etc.) that is created requires a Customer record to be created first. However, from a sales and marketing perspective, you can create a Lead first, with the view of "converting" the Lead to a Customer once the Lead progresses to requiring a Quote or other sales record.
Create a New Lead
From the main menu strip at the top, go to CRM > Leads.
Click the + New Lead button located at the top left.
Enter the Lead details.
Click the Save New button located at the bottom right.