There are two methods, depending upon the look you want.
If you cut off the top part of the growing stem, and leave the lower, it should sprout two new shoots from the node where it is cut. The issue here though is that the lower part of the stem gets less light and usually loses leaves, unless you have bright light and they are well spaced.
YThe other and more common method is to cut off the top part of the growing stem and plant the cut end in the substrate, pulling out the older stem. This keeps fresh new growth if this is done regularly; it may be needed every couple of weeks, sometimes every week, depending upon growth rate.
You can cut the stems at any node, but it is best to leave several leaves on the cut part. The leaves on the portion to be buried in the substrate can be pulled off.