Run a piece of unity from within a native android

Question

I'm doing an android app with some buttons in it. I would like to create a click event that when you click one of those Buttons ("see book Botton") a unity-vuforia app will start playing.

Here is the guide I tried to follow.

in step 2, I don't know where to add the script. I put the script in the script folder in Vuforia folder.

in Step 6: Build your native Android app and use above aar file as a library, I get the following error when I import the aar file: IDE error

I've tried everything and repeated the process several times for a week with different details changed, and don't understand what is happening.

Thanks for any help.