While there isn't an option to import bills in QuickBooks Online, I suggest going to the Intuit App Center. By doing so, you can search for a third-party app that can help import bill transactions.
The other option you have is to manually enter the data to record vendor bills. To do so, please follow the steps listed below:
Click the Create ⨁ icon.
Select Bill under Vendors.
Enter the information needed to complete the details.
Click Save and close.
Once you're ready to pay it, check this out: How to Enter and Pay Bills. Then, go to the Navigate the Pay Bills screen link for the detailed steps. Also, this article provides another way of paying what you owe to your vendor.
Drop me a line if there's anything else you need and I'll get back to you.