Unlike Windows, in a Mac you don't "Map Network Drives" and give them a drive letter. When a drive is "mounted", its icon is displayed on the desktop, whether a network drive, a USB drive, an SD card etc. To unmount it, right click and select Eject or drag the icon to trash. If you shut down and restart away from the local network, the drive won't be mounted and displayed. What you can do, when it is mounted, is to right click it and create an "alias". This is the Mac's equivalent of a Windows shortcut. This can then be used to mount the drive when in range of the local network.
As regards Outlook, go into the program's account settings and make sure the password has been entered correctly in there. May be worth deleting it and entering it again.
