Welcome to the Bunnings Workshop community @northland. It's fabulous that you've joined us, and many thanks for your question on propagating Poinsettias.
You can propagate them, and it can be quite an easy process.
Select a stem that has several small leaves, and that is quite pliable. New growth is perfect for this. Cut the stem just above the base of the plant. Strip off the lower leaves and apply rooting powder to the cut end. Fill a small plastic pot with a 50/50 mixture of sand and perlite. Create a hole in the middle of the mixture and place the cut end in. Backfill around the cutting. Do not just push the cutting into the mixture, as it will wipe the rooting powder off. Place the cutting inside on a window sill that receives morning sunlight. Mist the cutting daily to keep the leaves hydrated. When the top 30mm of the mixture becomes dry, water the plant and allow it to drain.
After 3-4weeks, you can check the cutting to see if it has formed roots. Gently pull on the cutting, and if it resists being removed from the pot, it likely has developed roots. Once it has established roots, you can plant it into a larger pot and then into the garden.
Please let me know if you have any questions.