How to setup the LinkedIn Ads integration
First, navigate to the home dashboard for the campaign where you'd like to connect the LinkedIn Ads integration. Then, choose "Ads --> LinkedIn Ads" from the dark navigation bar on the left-hand side of your screen.
Next, click the link in the middle of the screen that says "Setup LinkedIn Ads".
You will then be prompted to select the customer account which you would like to connect. Click the radio button next to the appropriate account, then click "Save".
If the account that you would like to connect is under a different LinkedIn Ads account, and you need to enter different credentials to access that account, click the button that says "New Account", then enter the appropriate credentials, and step through these screens again.