Download the demo from the internet (
www.rfactor.net -> try/buy -> download mirrors).
But apart from a total of 4 mods, 2 of which aren't public and one of which (at least) isn't finished it's completely rubbish.
Even the F3 mod, which was 'verified' by an F3 driver is so completely unrealistic in it's response and feel, let alone it's performance, that it just makes a mockery of the term 'simulation'.
Of course, that's just my opinion. I gather there is a large community of people who have never driven a real car who think it's the best thing since bread was cut up into thin bits for ease of getting it through the letter box.