When printing checks, how do I insert information for the Memo Line on the check?

It's good to see you here, Asmcgee710. I'll ensure you can print your check with a memo in QuickBooks Online. 

If you're referring to the Memo box section, you can input your notes or messages manually in this area, and they will appear when you print checks via voucher or standard form. Take note that you'll have to open the check individually to add a memo in the print check queue page.

See the sample illustration below:

Here's the actual view when printing your checks through Standard and Voucher form:

In the event of configuring print settings, here's an article that will guide you through the process: Configure your print settings for printing checks in QuickBooks Online.

Please don't hesitate to ask if you have any more questions about printing checks. I'm here to help! Have a wonderful day ahead!