How do I get them to drive the way I want them to?

No one learns effectively when they don't want to be there. Supervisory Drivers especially ones that are doing it for the first time don't hide being anxious very well. The learner driver will pick this up pretty quickly, are respond accordingly. Try to respond calmly to actions and instead of being reactive, try being proactive. As something is occurring around the learner driver, make them aware of it and ask them how they would or should get out of it. If they are unsure ask them how you would get out of the same situation. If the learner driver has seen it before they might be able to find a solution. If you need their focus to be on a sign, before you pass it, draw their attention and ask them to explain what it means to them. Even an "I don't know" will at the very least give you a talking point and something to work on. At least if the learner knows you will work with them as the co-pilot, things should get easier. If things are still worrying, change the situation until both you and the driver can manage the situation. If there is still concerns enlist the services of a driving instructor.