To start the metronome just clik on a time value, click on the red button to stop the sound. Click on the arrow to display another range of values.

For your information the standard tempos are:

LARGO is 40 to 52 BPM (*)
ADAGIO is 48 to 66 BPM
ANDANTE is 60 to 88 BPM
MODERATO is 84 to 108 BPM
ALLEGRETTO is 104 to 120 BPM
ALLEGRO is 120 to 144 BPM
VIVACE is 138 to 168 BPM
PRESTO is 160 to 200 BPM
PRESTISSIMO is 200 to 208 BPM

(* where BPM is "Beat Per minute")

This free version doesn't provide tempos lower than 45 BPM, higher than 170 BPM and intermediate values.