:confused;

I just signed up for the free trial of Adobe Contribute (Mac version) to make
regular changes to my website, and I need to know how to access my Cascading
Style Sheet for formatting (BF, font, color, etc) text. Adobe Support won't
help me with this, as I'm in the trial period (haven't bought the software
yet), but if I can't figure this out, I'm not planning to buy it! Does anyone
know how to do this. I'm sure this is simple, but having never used this
product and not being the most technical person, I'd appreciate any insight!
Thanks!

You cannot edit the .css files directly in Contribute. What you can do is:

1. in the main menu go to >Edit>Preferences
2. go to 'File Editors'
3. add .css to the files to be edited in Contribute using a so called external
application
4. add the application (f.i. notepad.exe) and make it 'primary'

Next you will have to adjust the users and roles settings:

1. in the main menu go to >Edit>Administer websites and choose your website
2. choose your role and click Edit Role Settings-button,
3. go to Editing and check 'Allow users to edit source code in external
application'.

To edit the css file:

1. connect to your website
2. click the Choose button on the right of the address bar
3. browse to the css file you want to edit
4. when the css file is open Contribute will tell you (This file cannot be
displayed in the Contribute web browser.
You may be able to edit this type of file with another application. Edit your
Contribute preferences to specify an application.)
5. normally you would now go to the main menu click >File>Actions>Edit source
code in external application, BUT you don't, you click >File>Actions>Edit Page
or the 'Edit-button' in the main screen
6. notepad will open the file, you can edit the file now, save the file in
notepad and then publish the file using Contribute.

Thank you. To confirm, will this work on the Mac version?

Yes, according to Adonbe there are only minor di9fferences in thee PC and Mac version, so you should be fine. Maybe some items are located in a different place.