Back up is a very important command to teach your llama because it teaches them to respect your personal space. It is also very helpful if you are walking in a tight space (such as in a barn) and don’t have room to turn your llama around and walk them straight out.
Most llamas pick it up pretty quickly by just giving some quick lead rope tugs downward and towards their neck. Once they have gotten good at backing up you can try adding in steering by tugging their lead to the left or the right, while still downward and toward their neck. If you are thinking of trying off-lead work in the future I would recommend always moving with your llama while you steer them so that you are always directly in front of them. This teaches them to keep their front with you and you will be able to steer them by just side-stepping while they are off-lead.