I have installed Ubuntu 17.10.
I have downloaded houdini-16.5.268-linux_x86_64_gcc4.8.
When I double click the INSTALL file all I get is a text document.
Which tells me to run houdini.install.

In OSX and Windows I can double click on a file to run or launch it. This does not seem to be the case in Ubuntu.
How do I run the installer?

www.sidefx.com/faq/download-and-installation/#faq3


Seems like you didn't extract houdini installation from a tar file (judging by the title of script editor in you screenshot). You first need to extract it, then double click on houdini.install or run the script from terminal (as explained in faq).

also, looks like you double click houdini.uninstall, not houdini.install

I have muddled through the install and I have Houdini up and running now. And you were right, I was running the wrong file inside of the tar. I am still getting used to the way Linux presents files compared to Windows and OSX.