Welcome to MobileRead Mike.
If you let us know what country you are from and what computer O/S you are using, it may help in our suggestions.
I would go browse
Sony eSupport for the PRS-650.
Once there, you can read and/or download the user manual for your reader.
You can also download the latest version of the Reader Library Version 3.3 and install it. This should create an Adobe ID for you (unless you already have one) and authorize your computer to read Adobe DRM'd ePubs and PDFs.
Then you could try purchasing some free books from the Reader Library and try viewing them on your PC to make sure you have the process working right.
Then you could see if there is a library near you which allows you to borrow eBooks and see what is involved in checking out an eBook. (I suggest you stick with the ePub format.)
The list goes on...
I had my Reader Library populated with dozens of eBooks before my reader arrived.