Ok, let's put your questions in a slightly different order (that is more consistent with what you are trying to do)
This depends on how you are installing WordPress. If you are installing WordPress manually, just follow the installation instructions and make sure you place the distributed WordPress file/directories into your "yourdomain.tld" (where "yourdomain" is the name of your domain, and ".tld" is the "top-level domain - .net, .com, .org, etc.) sub-directory of your user space.
If you are using either of the DreamHost "One-click" installers, the same thing applies, but you will not be able to do this if you already have files in that directory (the DH one-click installer requires the "target" directory be empty).
For instance, to install WordPress so that it is shown whenever anyone browses to darwinblog.com, simply specify that, without any subdirectory) as the target for the installer. At the part of the form that asks where to install ("Install to: Please be sure there are no files there now!<place for a subdirectory to be specified if desired), just select the "http://www.darwinblog.com" and ignore the following space where yuo could have defined a subdirectory. Again, note that the directory you choose must be enpty for this to work.
Assuming yuu have completed the step(s) above properly, and now have a WordPress blog running on http://darwinblog.com, you can configure that instance of WordPress to use the "About"" page (or any other page) as the "home" page for the blog by logging in to the admin section of WordPress and making the appropriate setting changes.
In the current version of WordPress (2.5.1) this is done from the "Settings -> Reading" screen, where the top section under "Reading Settings" shows "Front page displays" and offers radio buttons to make the front page either "Your latest posts " (which is the default) or "A static page (select below)" (with drop-down boxes for existing pages/or a given page of "posts"). Just select "About" from that list for the "static page" and save the form.