To record existing layaways, you would type them in from the layaway choice
from the Sales Menu -- very much like you would enter any other layaway.
If possible, it is better if you record the inventory items in the inventory
file before-hand (with a quantity of 1). That way recording the layaway
would take the inventory out of stock. If you have a particular reason for
NOT recording the inventory use on layaways, then you could use dummy sku
numbers. (each major code automatically gets one dummy sku number)
You should type in the original date of the layaway into the layaway screen.
As for layaways with multiple payments, you could either enter a single
lump-sum payment of the total amount paid, or you could just type in the
original payment, then apply subsequent payments to the layaway by choosing
option 4 from the Sales Menu, with each payment recorded with the
appropriate date. Entering each payment separately will take a bit more
time, but will give you a better history of the activity on that sale.
If you are already at the point where you are entering each day's actual
sales, and if you want to avoid mixing old layaway payments with the
payments from today's sales, you could run a Z report to clear the cash
register before entering old layaways, then record the old layaways, then
run another Z report to clear the cash register again to zero the register
for tomorrow's sales. If you are not yet up-to-date with sales, then you
needn't bother with these extra steps.