A quintuplet is much like a triad but consist of 5 notes in the place of 4 or 3.
You can make a quintuplet-note out of an ordinary note with the use of <alt-5>. Please note that you should always make sure that 5 quintuplet notes (or equivalent) are used together, to make a more common not-value . Quintuplet notes have durations like 1/10, 1/20 or 1/40, so 5 quintuplet 1/8 notes form one ordinary quarternote. You can promote a quintuplet note to an ordinary note by the use of <F6> just like you can with a triad-note