For offline payments they need to go through the normal frontend subscription process, select the offline payment method, then confirm the offline payment. When you receive their payment you can then pay it in CBSubs > Baskets. You can go through this frontend process on their behalf as an admin as well by viewing their profile first then following the same steps.
Renewing through CB > User Management doesn't create a basket and does not provide a means of logging an offline payment. It just directly gives them the subscription selected as it's for management purposes.