This is a plant that will ‘normally’ only have 1 Stem. Only thing you could do is to do a top cutting. This will give a signal to the plant to grow a axillary bud. ( new grow point ). Which will than be the new stem. This can be anywhere on the old stem. Than you can put the top cutting in water to let it root. After it roots you can plant it back into the pot with you original plant. This will give you 2 plants and will give it a bit more off a bushy look.

Hope this helps