Re: I need help setting up a google ads campaiign the gmail header
From your query, it seems like you want your ads to appear on GMail. (Please post back if that's not what you meant!)
To achieve this, you would need to have a Display campaign and use a managed placement to target GMail as a placement. It wouldn't necessarily be possible to guarantee your ad would show there all the time (or in the header on the GMail page), but this would be the best way to try and go about it.
Hope this helps a little!