Write down the lyrics from your song on a piece of paper. Go through the lyrics and place a slash above all of the syllables that should be accented and a horizontal line across unaccented syllables. If you have trouble with this, say the lyrics aloud and listen for the places where you accent syllables.
Create a rhythm based on the accent scheme from your lyrics. Don't think about melody at this point, just write down the rhythm without worrying about bar lines. Use a metronome to help you figure out if you should use an eighth, quarter, half or whole note by starting the metronome at a tempo of about 60 beats per minute and reciting the lyrics in tempo.
Recite your lyrics using the rhythm you created. Edit it as necessary to create a sense of flow from one syllable to the next. When the rhythm is finalized, look for the most important accents in the rhythm. Add a bar line just before the strongest accented syllables.
Count the number of beats in each bar and add a time signature to indicate any changes in beats per measure. For example, a measure that has a total of four beats, should have a 4/4 written at the front of the measure. Three beats will have a 3/4 and two beats will have a 2/4.
Sing your lyrics using the rhythm you created. Record yourself singing and sing the lyrics as many times as necessary until you have a song that appeals to you and makes sense according to your preferences.
Play back the recording to listen to the first note of your song. Find that note on the piano using a "hunt and peck" technique. Play the notes chromatically by starting on middle C and moving from key to key until you find the note that matches.
Determine all of the pitches from your melody and write them out with the help of the piano.