You assumed wrongly. I strongly suggest reviewing How to get started (there is no step-by-step tutorial) and the Rules documentation page. The answers to what you are trying to do now a will as the many hundreds more you will experience along the way are there. Blindly trying stuff is not likely going to ever work, especially if you have no experience with programming. You should always fires look to the docs and then look for examples.
For example, you want to know what the previous state of the item was? Rules | openHAB