You need a package already created for the shop — see Add Package — and the customer must already exist. If it’s a new customer, add them first in Business → Customer.
1
Click Assign Package
From the Service Packages page, click Assign Package to open the assign screen, showing every package already assigned to a customer.
2
Click Assign Customer and fill in the details
Save to assign it — the package becomes active from today and automatically expires once its validity period ends.