Adding google ad's to my site.

Hi, I am having trouble adding Google ad sense to my site header, I would like it just above my page tabs and below my site name, I would also like it right across the page like my bottom footer ad is. I know i need to add the code to the header.php but i’m stuck for where to place it, I did attempt it my self but it did not look correct and when i accessed it from my mobile the ad stretched out right beyond my page and looked stupid, Any help would be awesome as i am a complete novice at WordPress.

Thank You.
TruTech.

https://www.TruTechNoid.com