Hi,
JobRoller is a WordPress theme.In order to make it work you will have to first install WordPress on your server(2) and then upload and activate the theme.Most of the hosting companies allow you to install WordPress automatically with one click.
(3)JobRoller has an administration panel where you can set it, really easy to use, not requiring programming skills.
(4)The only thing you need to know is how WordPress and JobRoller work.This will require reading the documentation and practice.
Please check the administration panel
here.
Let me know if you have more questions about the theme.