in order to go to a specific page (in your case the Private page), saving also a parameter (e.g. the OID of a selected product), you should use a Jump Unit.
The Jump Unit allows you to jump to a specific point of the application. It is associated with a Parameter Collector Unit, which collects the parameter (e.g. the OID of the product) and specify the point of the application where to jump.
In your case, the jump to a private page can be implemented as following explained:
1- Insert a "Jump Unit" in the public "Site View" and a "Parameter Collector Unit" in the private "Site View".
2- Add a parameter to the "Parameter Collector Unit": right click on the unit -> Add -> Collector Parameter.
3- Select the "Jump Unit"; in the "Properties View" specify the property "Collector Unit" to the previous created "Parameter Collector Unit".
4- Draw a Normal "Link" between the result product list (e.g. the Index Unit) and the "Jump Unit", coupling the OID of the product.
5- Draw an "OK Link" between the "Parameter Collector Unit" and the target unit (e.g. a "Data Unit" which shows the details of the product) and couple the parameters (e.g. the collector parameter representing the OID of the product, with the key condition of the Data Unit).