Creating a new client within Swift Galleries is very simple. First, navigate to Clients, then New Client.
When you do so, you'll see a screen like this:
Client Details
The name of the client and/or session; the client will see this. Something like "Luna Family" or "Larwig Maternity". Make sure if you're doing multiple sessions for a client you decide how they're going to order. If you're doing a sales meeting after each session but you want them to be able to order from current and past sessions, put all their images into one "client" so they'll all be accessible in the Designer together, and that will also make them accessible during their sales meeting. If you want them to purchase from one session only, you can create a separate Client for each.