If you have the icon shown below, then Google Drive is installed. Just click on the icon and choose ‘Sign in’.
You will need to use your gmail user id. (email@example.com) That password is normally synced with your normal network password.
If you don’t have that icon, then go to Self Service and install Google Drive from there.
When you go to open it the first time, it will warn that you are installing a program from the Internet and you can click OK/Open. Then sign in with your gmail user id.