You can do this from two places, from POS or from a classes' details page.
To add someone from a class details page, click Classes > Schedule > click the class they'll be booked into.
Click 'Add customer into this class' > choose customer (note: if they don't have an account, click the 'plus' sign to add them)
If the customer has a subscription or class pack that applies to this class, it will show as an option. Click it to add them in using the pack or subscriptions.
To add a customer from POS,
click Home > POS > choose a customer > select class > choose the class > Add to Cart.
In the Payment section at the bottom, check to see if they have an applicable membership by clicking Membership. If they do, it will show as an option, but only if Membership is selected.
If they don't, this an opportunity to upsell, using the blue 'Pay with a new membership' button above. Choose a payment method and click Book.
