tony, I force them to grow side branches, by leaning the pot onto something, a brick? also, if it is as tall as you wish it to be, you pinch the top in addition to lean it. in a couple of weeks, you lean it the other side. Figs have apical growth, so removing that tip, other branches will attempt to dominate, thus initiating growth.
if you don't wish to lean the pot, you can tie the long branch to a piece of bamboo and slowly lean it to a side, you will see the side growth to appear.
the more you keep it leaned the more branches.
I am working on my new DK, it is almost 5 feet tall. I tied to a bamboo and am leaning the pot, so that the entire thing turns. I want to grow it horizontally.
Good luck.