Hi, Joyce. Do you have a copy of textedit? If so, just open textedit and open the document in the wordpress folder you downloaded named 'wp-config-sample.php." If you have OS X or above, you definitely have TextEdit. Make the changes and save.
Now about those database details that you need to change when you're in TextEdit...my host is MacHighway and it wasn't too hard to find, but I don't know about other hosts. Have you found the control panel? If you don't know where the control panel is, your host has been remiss :-) Ask them for it.
If it isn't clear where to find the info you need, contact the support team at your host and ask how to set up a database (if there isn't a wizard in the control panel), and how to get those details. Copy and paste the info from the codex into your query to support - they should be used to these questions. Do mess around in the control panel first, though. A lot of it you can figure out.
I know it all seems like an alien language, but you'll get there. Let us know what happens next.