collect the lights you want to use.
I choose these, because a big ol' frame fell on them several times, smashing the light casings to bits.

If necessary, take off any casings, until you're left with just the string of lights, like so.

Use your box cutter to cut 1 cm by 1 cm x-shaped slits through which you can 'shove' your lights. One slit per light.
Choose the placement of your slits strategically, according to the picture in your frame, so that the light makes sense, you know?

Voila, strategical placement...

Next, plug in your lights to admire the result.

And hang it somewhere near a socket.

Take your time to admire the outcome, after all, you did it all by yoursels.
I'm so proud!