Go to Clients and choose "Add Client". Enter their name and email (a phone number is optional), and you can assign them to a group. Clients are added one at a time from here.
Click any client to open their profile. You'll see their contact details, notes, body-metric charts, assigned packages, booking history and payment history, along with totals such as their overall value and the sessions they've used and have remaining.
From a client's profile you can archive them to hide them from your active lists, or remove a package you've assigned — its remaining sessions are then deducted. There's no separate freeze or pause; access is managed through the sessions in each package.