help me please

i want to add favorite button. How will i do?

MITs tutorials    http://appinventor.mit.edu/explore/ai2/tutorials.html

AI2 free online eBook   http://appinventor.mit.edu/explore/ai2/tutorials.html   ... the links are at the bottom of the Web page.

i want to add favourite button.

what exactly does that mean? can you elaborate?