Open a terminal at the location of the main Twine file, and enter
./Twine
It might be different for you, but I had to install "libnss3" before I could run Twine.
If you don't want to run it from the terminal every time, you can create a clickable shortcut on your desktop by first going to your desktop, right click and select "Create Launcher".
Name it whatever you want, probably "Twine 2" .
In the command section put "./Twine" without the quotes.
In the working directory section, put the directory of wherever the main Twine file is located.