If you aren't used to riding on roads with cars, that's OK. You will be soon. But you should look up the traffic laws in your state and locality that pertain to bicycles, so that you know what your rights are and have some idea of what you are legally expected to do in various situations.
If you're unsure or aren't confident about riding in traffic, there may be classes in your area for adults to learn exactly that. The League of American Bicyclists has some programs, and some bike shops (particularly more urban ones) may have classes or know where to direct you.

Most of the details about what to wear, whether you need to change clothes, what to carry and how to carry it, etc, are things you'll figure out as you go. FWIW, for all the discussion of showering and changing, lots of people are perfectly able to bike 8 mi to work and be ready to work when they get there, no changing required. Unless you work in an office with a very high-end dress code or you really sweat a lot, you probably will be fine without changing clothes or with only changing your shirt or something.

But yeah, no need to over-complicate.... in order to ride your bike to work, there are only two things you actually *need*: a bike, and a job located at least ten feet away from your house.