Pot of Coffee
Have a pot of coffee handy as it will keep you going for the length of the day. You will need to be attentive and although caffeine is only a short term solution, if you need to do something in such short notice, it will be the thing to do. If you are a tea person, that will also do.
Make a List
Since you cannot learn everything in 24 hours, make a list of what you think you need and is important. This list will help you in learning the most needed basic tools. Make sure that you have essentials on the list and try not to add advanced level skills that actually require days to learn and weeks to practice and perfect.
Find an Expert
It may be much more difficult to read and apply in such short notice so grab a friend who knows the software and get working. You will have to bug this person until you get the required information out of him or her. You can probably learn the same thing in half the time when someone is actually showing you how to do it.
Doing so will help you in practicing as you learn. You can watch a tutorials online and practice along with it. This will not only be a quick way of learning but will also give you the confidence that you can do it as well. Make sure that you practice more than once so that you can do it later on as well.