In order to mount a container first chose the container file in the line labeled "Container:". This can be done by directly typing the files path name into the line or by browsing the file system with the Browse button at the end of the line. Similarly you must chose a mount point in the line labeled "Mount Point:" below the container line. On Linux mounted file systems are not administrated by drive letters as on Windows systems. Instead they become part of the hierarchy of directories. The—existing and preferably empty—directory under which the new file system will be presented is called the mount point.
The radio buttons labeled "File System:" can be left on the default "auto" which means that the container will be probed for the right file system. If the radio button labeled "none (don't mount)" is checked, the container will be decrypted but the file system inside will not be mounted when the Mount button is pressed. This only makes sense for special administrative purposes. There is also a check box "Mount Read Only:". If it is checked the container will be opened for reading only and all write accesses to it will be denied.
When you press the Mount button you will be prompted for the passphrase if it hasn't been entered beforehand by the Passphrases menu. The passphrase dialog presents four lines for the passphrase. The passphrase must be entered there in the same way it has been set when the container was created or when the passphrase was changed.
In order to unmount a container simply mark it in the list at the bottom of the main window and press the UnMount button. You can also mark several or even all containers in the list and unmount them at once by pressing the UnMount button. Of course you can only unmount the containers you have mounted yourself. For these containers your user name is presented in the Owner column of the list. Other containers are ignored by the unmount procedure.