I have some checks to vendors that I want to apply to bills, how do I do that? The checks are expensed to Accounts payable

I'm here to help you out, hihiroombooks.

To link a check to a bill, you have to create a Pay bills transaction for the Vendor. I'd be glad to show you the steps.

If you don't have a recorded Bill yet. Follow the steps below:

1. In you QuickBooks Online QBO company.
2. Go to the Hamburger icon and select the +New button.
3. Select Bill,then enter the Vendor's name and the other details. 
4. Hit Save and close.

To link a Check to a Bill, create a Pay Bill transaction. Here's how:

1. In you QuickBooks Online company.
2. Go to the Hamburger icon and select the +New button.
3. Select Pay Bill, then enter the Vendors's name.
4. Tick the box for the customer's name and verify the amount.
5. Hit Save and close.

Here's how it looks like.

For more information, check out this article: Record vendor prepayments or deposits for prepaid parts or services.

For future reference, this article can be helpful in voiding check payment in QuickBooks Online: Void or delete a bill or bill payment check.

Let me know if you wanted to ask further assistance. I'll be here ready to back you up. Take care.