You can't just type Glest, that message is telling you to get Glest from add/remove, which you said gave you problems.........
Open Terminal.
Navigate to the directory where the Linux installer installed Glest.
Command: cd <|full path to installation directory|>
List all contents, the long way.
Command: ls -l
Please copy the list out of Teminal and post it.
To copy: Ctrl + Shift + c
To paste: Ctrl + v
Leave your Terminal window open.