help with installation

Have you watched the video and read the description of the plugin. You basically just have to copy paste codes inside Ad Inserter plugin and only have to change the Adsense code part.
It is quite easy. Check out this video: https://www.youtube.com/watch?v=XKSeT4MIBBg and this support thread: https://ww.wp.xz.cn/support/topic/does-this-work-with-ad-inserter-plugin/
Generally, you don’t need to write any custom code.