To register an individual who does not include payment with their registration, follow the steps in how to register individuals.
You can add an individual as an attendee and even register them for events without them including payment simply by putting "PO" in the payment type on the event screen. "PO" will tell the system the attendee owes a balance.
When payment for the event comes in....
You can access the payment information for attendees two ways:
attendee/locate the individual/right-click/payment OR
file/payments (under the meeting section) either way you access the same screens
To add a payment....
F8
or the add button 
Type in the ID number (the events for that attendee will automatically fill in the left window)
Enter the payment date (space bar for today's date or type in the required date)
Enter the payment amount (these are the minimum, you can complete the rest)
Spread payment if the attendee is paying for all outstanding events.
Pay selected if the attendee is only paying for one of multiple events, you check it in the box.
Save
