Cut the stickers to small size that will fit on the piano keys with a pair of scissors or paper cutter.
Make a chart showing which color will be which key. Start with C, and work your way up the scale. You can use a piano key chart to show you which keys correspond to certain notes, but the basic scale is simple. The lowest note on the piano is a C, and it moves in ascending order. The scale is C, Db, D, D#, E, F, F#, G, G#, A, A#, B. Once you reach B, the scale begins again with C.
Write the names of the notes on the appropriate stickers with a waterproof marker. Make sure the ink has dried before placing the stickers on the keys to avoid in seeping through the paper and onto the keys.
Place the stickers on the appropriate keys, starting with the far left note on the piano. You can either continue placing C notes on the appropriate keys by noting the position of the C keys, or you can put the stickers on each ascending note following the list of notes above.
Purchase a book of basic piano scales that you can practice. Learning the basic scales is very important, as it will make playing actual songs much simpler. Practicing the scales is also a great way to memorize the patters of the notes and help increase your muscle memory. The most important scales to focus on are the major scale, minor scale, major pentatonic scale and minor pentatonic scale.
Get a book of very easy piano sheet music or piano tablature. While playing songs like “Mary Had a Little Lamb” may not be your ultimate goal, the practice will definitely help you to remember where the keys are.
Practice at least one hour per day. With most instruments, learning is part rote memorization and part muscle memory. Without sufficient practice, it will be very hard to master the basics of piano playing.