Just play the songs of which you find the sheet music: e.g. search for the title among images.There are 1000s of melodies - also with chords. Start with the most popular like folksongs and children songs, even baby songs, or simplified tunes of symphonies. So you will train reading melodies and sight reading and get an idea of chords and fitting melodies. Then you can look for songs on youtube tutorials with or without chords and play along. You will train your ear and sens for harmony and melodies. Finally you will be able to play along every song you like and accompany it with chords.
But there is now way to find the melody of chords, if you have only the chords and don't know the tune.
And you will have to study a lot about triads, chord notation, inversions, progressions etc.
example images:
searching for Joyful in images
