Adding Ads Under Menu Items (WordPress Site)


Hi All
I hope this is the correct spot to get help for my issue.
I have a wordpress website, and want to add my google text ads directly under my Menu items.
https://growingchillies.net/

I'm not the most experienced with wordpress theme customisation but am hoping someone can quickly explain where i need to modify my theme/css to insert some text adds.

Note, ads to appear directly under Menu Items (Home, Chilli Seeds, Chilli Readers Reports, etc)