Here are a couple tips:

To avoid buzzing-Don't press the string down exactly in between the metal frets, but closer to the fret towards the body of the guitar.

To avoid muffling strings- Press with your fingertips. Try to bridge over the other strings.

Don't like the pick? -For now, try strumming without one. Brush your finger across the strings or use your thumb. In the next lesson we'll focus more on using the pick.

Before you go on to the next lesson, memorize the A, D, and E major chords.