How do I add vocal melody in a guitar chord progression? Are there any rules I must follow such as only using certain notes in the melody for each chord throughout the chord progression?If so how do I do so?
Unfortunately, there is no easy answer.
The thing about music is that it is very subjective and artistic. To be honest, there are no hard and fast rules! The closest you can get to rules is learning music theory (more on that in a bit), but all theory gives you is rules of thumb. These chord progressions are usually effective; these types of melodies usually sound bad - but not always, and sometimes the unconventional or "wrong" approach is exactly the one that a piece needs to sound effective. For example, one of the rules of thumb is that a melody should end on a note in the final chord, but I recently wrote a very peaceful and happy ambient piece that ends on a note a minor second below the final chord's root, and the effect is even more relaxing in a way than had I written a melody that "followed the rules."
That said, if you want to know how to go about writing melodies for a given chord progression, there is absolutely no alternative to having a basic knowledge of music theory. If you don't know music theory (you know guitar chords, so you probably already have a good foundation), I recommend going through this site: http://www.musictheory.net
If you already know music theory, these two rules of thumb should help you get started writing melodies, but remember that you can ignore them whenever it benefits your song:
In general you want the notes you use in your melody(voice melody) to reflect the chords you play. For example if you play a C major chord you want the melody to use the notes of the C major chord (C, E, and G).
This works in theory, however if you just used the notes of a chord in your melody it would get pretty boring fast.
Nonharmonic tones are used to embellish a melody. The simplest two I would understand before diving deep into the subject are passing tones and neighbouring tones.
A passing tone is a nonharmonic tone(not part of the chord) that is sandwiched between two notes of a chord. Using the C major chord again if the melody was to go from C to D to E the D would sound fine and be considered a passing tone.
A neighbouring tone is above or below a note and the next note is the same one as before. Using the C major chord again if the melody was to go from C to B to C the B would sound fine and be considered a neighbouring tone.
There is a lot more to this, but if you can understand that much you will develop a melody that sounds good.
As some of the previous comments have suggested, your post is somewhat vague, but perhaps I can help shed some light. If you want to add melody within a chord progression, play some of the notes near your chord that are in the correct key!
If you want the melodies in your chords to match your vocal or instrumental melody, there are numerous ways to approach this. Analyze your melody and determine where playing a chord sounds good and then play the single melody notes or thirds, fourths, or fifths, if you want to add some additional harmonies. This will require a bit of thought and there is no easy way to put it into words. You can try to play chords over every note in your melody, but that could turn into a disaster, and may very well overwhelm the listener.
You mentioned guitar, so an excellent song that I can suggest for you to listen to and learn is "Norwegian Wood" by The Beatles. It is a wonderful tune, and not difficult to learn. The guitar follows the melody very closely and the main 'riff' is centered around one chord, where the melody notes are all very close by. I highly suggest that you listen to and learn this song and see if that's what you're trying to do.
If you want to hear and learn a song that has a unique guitar melody that compliments the melody, listen to "Mother Goose" by Jethro Tull. This one is much harder to learn, but it showcases the potential for counter point and again utilizes chords and notes that are generally close by and make for interesting guitar pieces.