First you will want to click the gear cog at the top right and go to Quickbooks section, under Quickbooks "Setup"
Select the Quickbooks Account Type to Online
Be sure to click Save After
Click the QB X drop down and click Connect TO QB
Sign in on the pop up with your Intuit Quickbooks Online Account Information
Upon Agreeing to the terms and conditions with the integration after signing in, you will get a pop up that says you are connected and can close the window, and you are all set!