To install Celtx on your Linux computer:

1. Download the appropriate language file to your computer.
2. Right click installation file and select 'Extract to'.
3. Then double click the celtx file inside the celtx folder to launch Celtx.

If you want to make it available to other users on the machine, you can move the celtx folder into /usr/local. If others have trouble running it, you might need to right-click on the celtx folder and check that other users have adequate permissions (read and execute) for it and its contents.