Have a look at the contents of the following link, it will show you downloadable manuals for Step 5 that will prove useful for your work.http://support.automation.siemens.com/WW/view/en/10805348/133300
The first manual you find, simply titled Step 5. is a tutorial showing step-by-step how to create, program, download and test a sample project (automating a carwash) in Step 5, specifically for a S5-95U. Instruction lists may vary for different processor families of the S5 family, but the basics of the Step 5 programming environment are well described.
I recommend that you start your learning of Step 5 by following the sample project as defined, it is the best way to learn all the details of navigating through Step 5. Whatever time you spend on this exercise will be worth it when you start your own program, For example, the basics of creating a new project are shown in chapter 2, simply follow the steps as the tutorial develops.
Hope this helps,