This is a brief and spare method for learning chord melody for playing songs.
I am not going over learning chords, reading music, jazz style, etc.
Get some easy sheet music. A book of popular songs for clarinet is good. Easy pop tunes that have familiar melodies. Forget playing chord melody with AC/DC or Metallica.
Pick a tune you know the melody to!
Note the key signature of the tune. Mentally review the chords in that particular key. Look for key signature changes in the song.
Take the first note in the song and arrange it as the top note in a chord from the key of the song. The note should be on the highest string (the B or high E string on the guitar) and should ring last to emphasize the melody.
Go through the song and do this for each note. Use chords you know. If you can't think of a chord then learn more chords. Drop 2 chords are handy for chord melody but you can use any chord shapes that harmonize. Use 7th chords or chord extensions if you like. Use chord substitutions if you like.
This is a very slow process at first depending on your chord vocabulary and sightreading ability. Learn the notes on the treble clef. Generally it is a good idea to put a chord under at least the first note in a bar. Do whatever you like however.
It will take some time to develop proficiency. Much time.
Your sightreading will improve. Eventually you will be able to create a chord melody practically on the fly. You will learn to improvise with chords. You can solo with chords.
Much time is required. Enjoy the journey.