First, navigate to the campaign where you'd like to connect the GatherUp integration, then click "Integrations" from the menu on the left side of the screen.
Click on GatherUp in the list of available integrations.
Then click Connect New Account.
In the window that appears, enter the Client ID and API Key for your GatherUp account. If you're not sure where to find those credentials, please see here or contact GatherUp support. Once you've entered your credentials, click "Save".
Next, select the client you want to connect and click "Save".
If the client that you would like to connect is under a different GatherUp account, you will need to enter different credentials to access that account. To do so, click the button that says "Connect New Account" and follow the above steps.