WHAT IS IT?
A member of the guitar family of instruments which uses four strings tuned to a variety of notes. The tone and volume of the instrument varies with size and construction. Ukuleles commonly come in four sizes: soprano, concert, tenor, and baritone.
WHERE DO YOU GET IT?
Since we've spent so much time in the chilly lands of the north it will be a happy feeling for all involved to know that we'll be paying a visit to Hawaii  and their sunny sea kissed shores.
USING IT IN REAL LIFE:
Grab a Youtube account. Apply yourself to learning enough chords and then begin posting videos. 
USING IT IN WRITING:
I'll be frank. the ability to play the ukulele is not something that the fate of the world is ever going to hang upon. 
If the hero of your tale is in school then the uke might be a targett of the bullies who break it and then laugh at his tears.
the love interest may require a balcony scene.
In extreme circumstances your uke can be used as a well tuned club. Once it meets the head of the baddie it will give them an opportunity to escape 
MIGHT ONE TAKE OVER THE WORLD WITH IT?