Need help

Plugged this into battery for the first time and I got a spark and smoke came out , I checked for continuity with a multimeter before plugging it in and it passed the test. I am just curious to what my mistake was and how should I go about this going forward . Thank you

Plugged this into battery for the first time and I got a spark and smoke came out , I checked for continuity with a multimeter before plugging it in and it passed the test. I am just curious to what my mistake was and how should I go about this going forward . Thank you