any time now really. remove a non flowering 'shoot' all leaves and pull it off where it joins the main stem. you should have a small 'spur or heel' of older material as well.
dip this in hormone rooting powder and pop into good compost. cut the foliage off by half and keep barely moist. should work well.

I will have a go. Thank you for the advice. How long should I keep it before I plant it in the garden?

i suspect at the begining of spring, unless well rooted by september.

Thank You