To teach yourself to BEGIN to improvise, you need to start with melody.

Wherever you are in terms of knowledge, or experience is where you start. IE, the knowledge you have now, is what you start with.

In practical terms, I would suggest you start with a song, any song you know.
Since it's christmas season, you could start with a seasonal song: play the melody.
NOT from music , Not from tab, but from your own familiarity with the song.

If you are not comfortable with anything beyond 1st position (ie, first four frets of guitar) find the melody there.

RichM