One way I've found to get used to practicing with a metronome is to use it with exercises rather than with tunes, for example with the beginners etudes that Pierre has available for download on the sheet music page. Since there's no melody, I have no preconceived beat going on in my head, and am able to concentrate on just playing the notes to the tempo of the metronome, and practice getting my note lengths correct. Once I'm playing in synch with the metronome, if I play a wrong note, or lose my place in the sheet music, it's easy enough to keep in rhythm by just playing the last measure again until I regain my composure and figure out where I am. Practicing in this way, I'm learning rhythm and to read music at the same time, as well as practicing my fingering and bowing.