Again problems with apk installations via itunes..?
Apple had removed that app section in the latest version of iTunes 12.7 [released on September 19th 2017]. So there after this simple drag and drop solution as in the post Where in the world are the apps in iTunes library? helped to rectify the trouble.
But installing from the iTunes is not working for some times even with this drag and drop solution
I got a solution for this from Apple support site itself. Just go to this link and download the iTunes version Apple released
https://support.apple.com/en-us/HT208079
This itunes version can be used to download your app. And with this the previous App section is back in our ITunes folder.