Nice guide
Nice guide, however you should probaly have mentioned how you can trace the sprites if the background isnt transparent, and thus enable you to click on the sprite you want without selecting the background aswell.
Incase you dont know how to do this, follow these steps:
1. Import the sprite sheet to the scene.
2. select the sheet and go to Modify>Bitmap>Trace Bitmap
3. Adjust settings to your liking (pixel setting gives the roughest trace).
4. press ok and done, the background on the sheet is now deletable without deleting the sprites within it.