This step is really self-explanatory: get the words onto something that will stick to your board.
If you're going to laser cut your magnets*, you'll want only the outlines of your letters with no fill. I cut at 20% power to score the vinyl enough that it can be peeled off the magnet but not so much that it cuts all the way through.
If you're printing, make your files and print to the magnet sheet.
If you're drawing onto the magnet, draw on.
If you're sticking cardstock or something to the magnet, do that.
Because not everyone has a magnetic surface in their classroom, I'd be curious to hear other ideas for affixing these words to your board. Maybe velcro on a cardboard sheet? Thumbtacks in a corkboard?
*Which you really should not do because of the horrible, no-good, very bad things you may inhale as a result of burning vinyl.