How do I post a partial payment that was made online to the vendors website, to my vendors bill which now states "Schedule Payment" or "Mark as Paid"?

A pleasant day to you, wgkimble,

You can post a partial payment by navigating the Pay bills screen. Then, enter a partial amount paid to the vendor. Let me show you how:

1. Click + New.
2. Under Vendors, select Pay Bills.
3. Select the appropriate Payment account and enter or verify the Payment date. Use the account from which you pay the bills. 
4. If you select a checking account, verify or change the Starting check no.
5. Mark the checkbox for the bill to pay.
6. Enter the amount of the payment to be applied to the open bill. If available, you can specify the amount of any credit to apply in the Credit Applied column.
7. Select Save and print, Save, or Save and close.

The option "Make payment" has been changed to "Mark as paid" for customer on the Melio bill experience. So going forward, you'll select this when going to make a bill payment within the bill screen. 

Check out the A new embedded bill pay capability in QuickBooks Online and QuickBooks Online Advanced blog to explore new ways to help manage your outgoing payments.

Let me know if there's anything else I can help you today. I'm right here whenever you have follow-up questions.