How do I build the site after installation?

as I understand it, to put up a wordpress website, I need to get a dot com, set up a hosting account with someone like BlueHost, install wordpress, and I’m good to go.

Pretty much, and BlueHost has the SimpleScripts service available so can just sit back for a minute or two and then get your login info via e-mail.

My question is this: How do I actually work on the site once I get wordpress installed on the host server?

After logging in, you will be at the Dashboard “behind the curtain” where all the buttons are located.

How do I get the wordpress login screen that allows me to create pages, etc.?

Logging in will put you right at that Dashboard.

Do I have to open a browser window and enter the site URL to get the login screen?

The initial e-mail from SimpleScripts will include a link for you to either click to open a browser window or to copy into one you already have open.

Do I have to “park” the site or something while I’m building it, or how does all this work?

If there is a lot you want to do before anyone visits your site, there are ways to put it in maintenance mode until you are ready for others to see it.

How do I work on the site once I have wordpress installed?

The Dashboard for content, and there are various ways to do work on your theme if you might decide you want to customize it. But the first thing you will likely do is try a few themes to see which one you might want to use as you begin.