To connect your advertising accounts to Funnel, select Data sources in the left-hand navigation bar:
Hit "+ Data Sources" to open up the ad platform selection popup:
Find the advertising platform you want to connect to and follow the instructions. How to connect may vary depending on how Funnel integrates with each platform.
If you can't find the advertising platform you're looking for you can add it. Scroll down to the bottom of the popup and hit "+ Data request":
Each advertising account you add will show up on the Data Sources view. You can see their respective status, remove them as well as reconnect them if necessary.