Choose "Website" and paste in the generated URL for your project from the phosphorus site above.
Name your app
Choose/Upload an icon
Add a description if you want, but to test, this is unnecessary
Click Download on the right side, (preview may or may not work, don't worry if it won't preview)
It will download a .apk file, this needs to get loaded onto your android device, Dropbox or Seafile are the easiest, USB transfers work too.
Copy the .apk file into Seafile/Dropbox/USB
Open Seafile/Dropbox on the android and find the .apk file
Touch it to download it
Touch install when prompted (You may need to enable "Install from unknown sources" and try again)
Open the game on Android and test
Note that since it is Android, and scratch has no idea that it will become a touch app, you have to use things like "Follow Mouse" and "Click" or "Right Click" in addition to regular collision detection.
Make the sprite follow the mouse/touch: https://wiki.scratch.mit.edu/wiki/Making_a_Sprite_Follow_the_Mouse