Wax flower is generally considered to be a "filler flower". This means it is used to accent other larger flowers. Other filler flowers include baby's breath, statice, limonium and solidago.
It has a slender, woody stalk with tiny spiky greens. I usually strip off a lot of the greens to leave a bare stem, because this flower can shed on your cake if you aren't careful.
Snip your stems into smaller, manageable lengths.
Run your fingers over the flower, removing any loose greens.
Tape a wooden toothpick at the stem like you did previously with the other flowers.
Create a variety of sizes - don't make every single one the same length.
Always leave the bare wood of the toothpick at the bottom for insertion into the cake.