How use an epub file?
Being an industry standard file, there are a lot of applications you can use to read epub files.
For PCs (including Macs, Linux, etc.), I recommend Calibre software. It supports both epub and mobi formats.
Whether on Android or iDevices, I suggest Google Play Books.
Not all readers are the same. I tested on several and a couple did strange things with the formatting. What you want to see is something formatted properly like what is shown below.
