So would anyone know how to go about getting various companies to alow you to use there product in a film???

A product placement is when the company pays you to have their product in your film, a form of advertising. If you want to clear the right to use someones product in your film, you need to contact them and get those rights. But, if you look at the previous thread about this, chances are you do not need this. Unless you're film is going to be nationally distrubuted to 1,000+ theaters I really would not worry about this. And I have a feeling if you are posting here you are not getting much more distribution then a few friends and maybe a local film fest (Not to be an ***, just stating the truth)