1) Add “Sharethrough” as an allowed source for your account
First, make sure you are looking at the account level view.
Then click “Settings” button on the right.
In the Account settings, all SSPs are enabled by default - thus in the “Allowed” column. Sharethrough is one of them. Of course, you can unselect other media sources by moving them to the “Available” column, making every campaign under that account run only on Sharethrough.
2) Add Sharethrough as a source to a specific ad group
Go to the ad group and then go to “Media Sources” tab. Then click on “+ Media Sources” orange button. Click on “Sharethrough”. Sharethrough will now be added to a list of active media sources for this ad group.
3) Enable the Sharethrough source in a specific ad group