Go to https://github.com/danielchatfield/trello-desktop/releases.
Download the last version based on your operation system.
Unzip the zip-file in a folder (i name it "trello").
Go to the folder and open your terminal in it.
(open up your terminal and do "cd" to trello directory)
write this command in terminal:
    $ chmod +x Trello
Now just run it by typing this command in terminal:
    $ ./Trello