Once you export/save your ADIF files to Google Drive, you then need to go to the POTA and STOAS websites upload page, e.g. Parks on the Air | POTA
and select your files.
Now you need to be aware that small form factor devices like phones and tablets will not immediately make this option visible on the device.
You will need to enable the Desktop site as a browser option. and turn your device to portrait. Clicking the "Click here or drag button, will allow you to navigate to your exported adif files.
OK well there’s no such thing as drag and drop on an android tablet/device.
It also says “Click here”… Tapping the area which says drag and drop actions the selection as you see it.
You may need to go to app settings and enable Google Drive as a shareable, or click the hamburger menu to add Google Drive to the share menu.
You may need to google “android how to get google drive on the share menu” for more instructions
Alan