Firstly, you must have the app itself installed (AutoFollow), if you have installed it, Please go back, download the .apk and install it on your device.
Now onto to the setting up procedure, firstly, you'll need to turn on Developer Options. If if doesn't show in the Settings menu, go into "About" and tap the "Build Number" simultaneously till it states developer options is now available.
You will need to switch on Developer options, once it's switched on... You will need to select "Pointer Location" as seen on the image on the left. This is to determine the tap locations as devices have different screen resolutions.
Next step is to open Instagram, if you are wondering which instagram app this is, go to the home page, select "View All Apps" and then download it from the "instagram" tab.
Now once Instagram is open, you will have to hit explore, and search for "Instagram" as it's currently the leading profile with 54 Million followers.
You will then need to tap and hold the follow button, and then you must write down the x and y coordinates, like in the picture, I will have to write down. X = 715 Y = 426. Then you will need to open the Auto Follow app.