To get traffic from stumbleupon you'll need to signup for a stumbleupon account and then connect with other stumbleupon users.
Next use stumbleupon yourself to stumbleupon other content. Then share your own content on stumbleupon and be sure to use stumbleupon regularly to gain more traffic.
If you work hard and use stumbleupon often enough then stumbleupon can bring your website a lot of website traffic.