I want to apply the money in prepaid income account to individual customers accounts. how do I do that since the deposit was post and reconciled in previous months?

Let's apply the deposit to the individual customers' accounts, felice777,

You can start by opening the deposit and categorize it under Accounts Payable. Doing this will allow you to link the payment to the invoice.

To do so, the following steps shown below will guide you through:

1. Go to Accounting from the left menu, then choose Chart of Accounts. 
2. Locate and open the account where you deposit the payment.
3. Find the deposit, then click it to open then Bank deposit screen.
4. From there, change the account to Accounts Receivable.

Once done, navigate the Receive Payment page. Then, record the payment from there. Let me show you how:

1. Click + New.
2. Under Customers, select Receive Payment.
3. Select the Customer's name.
4. You should now see all open customer invoices and outstanding credits.
5. Add the Payment date.
6. Under Outstanding Transactions, select the Invoice you need to mark as paid.
7. Under Credits, select the Deposit entry.
   
8. Click Save and Close.

Check out the How to link a deposit to an invoice page to learn more about the process above.

Upon sharing this solution, I still suggest consulting your accountant. He/She might have specific instructions since making changes to the reconciled transaction will affect the balance on your register.

Stay in touch if you have follow-up questions. I'm always around whenever you need help.