Select Register Closures.
Select Close Register.
Select Continue to start the closure.
Enter the cash in the field called "Record and cash added to the till(non-sale) added.
Select Yes to confirm you counted $100.
Scroll down and enter $100 as the closing cash float.
Check that the cash to deposit shows $0.
Select Save Closure.
On your next register closure, you will see that the $100 shows as the opening float.
You can change the float amount in your next closure if needed.