you have to make your site as incentive type. i think sites that you were accepted under have to review you again. its kind of a hassle.
If you already have a CJ account then you need to amend your site under : Account -> Website Settings. You need to add an incentive/special program to your site. Then after your advertisers have reviewed your programs you basically use the SID (SmartRewards) tracking code at the end of your affiliate links. You will need to somehow need to generate the means to track your customers who are clicking on the links to be able them the incentive/reward you have in mind.
In that case go to Account -> Website Settings. Add you to the incentive plan how you intend to award potential customers. Each advertiser you currently have plans with will have to review their relationship with you to see if they happy to allow you to offer your customers rewards. If you go to CJ help and search for SmartRewards then it will explain to you all about it. Basically you will need to generate a unique id to your members being referred to the merchant dynamically on your server, CJ themselves cannot generate this for you.