This video introduces a couple of concepts that are key in constructing chord melodies.
1. The fewer the notes in the chord voicing, the easier it is for individual notes to stand out which is a goal in creating melodies. Occasionally it's appropriate to use all six strings, but generally I try not to.
2. The top note is the melody note. This is what the listener will hear as the melody. Creating chord melodies is really all about putting care into choosing the top note.
If you have any questions, post them below and I'll do my best to get to you! Cheers :)