Via the Web
Manage your OneDrive through your Office365 online portal here. You can use the Word, PowerPoint, and Excel Web Apps to create and edit documents from any device.
This is your best bet from a Mac.
"O" Drive on Windows machines
When you log in to your computer you should see a script window briefly as the OneDrive Mapper runs. You will be prompted to enter your DCS email address and password.
There will be a progress bar in the lower, right-hand corner of your screen to let you know it is still running.
If, after you have entered your password, another password box pops up, the password you entered is incorrect. Try to login to your Office365 in a web browser to confirm that the password is still valid. If you cannot login either place, you need to have your password reset.
The blue progress bar in the lower, right-hand corner will disappear when the mapping is complete. At this point you should have a Drive O on your computer, which is your OneDrive file storage attached to your computer.
Open your File Explorer. In the left sidebar you should see This PC. Click on this to reveal your mapped drives.
Directly in Word, PowerPoint, and Excel
In the upper, right-hand corner of Word, PowerPoint, and Excel is a "Sign In" link. Click it, sign in with your Office365 / Email credentials, then you can save, open, and edit your documents directly from OneDrive in your installed Microsoft Office applications.
There are also free apps from Microsoft for OneDrive in both the Apple Store and Google Play.