Hi Subreport itself is a report. What you are trying to do is not clear but still proceed as below.
1. Create the main report
2. Create second report (this your subreport)
3. In the main report , from where you want to navigate, right click -->Properties
4. In the window opened click to "Action" , click to Go to report radio button
5. Select the Second report from the list , then map the parameter.
Once you run the main report and click the field where you gave the above action it will open the sub report.