Okay, After reading documentation, this can be done by enabling "Pretty URLs"
This can be achieved by:
Dashboard -> System and Settings -> SEO and Statistics -> Pretty URLs
You then get a dialogue which has a tickbox, select it and click SAVE.
C5 should be able to rewrite the .htaccess file. If it is unable to do so, it will give you an error, and you can copy and paste the text generated in the next screen, to add to the file manually.