Can you please specify which Reporting Tool you are using to create the report.
If you are using Report Builder you can follow the following procedure
1. Open Report Builder
2. Click on blank Report
3. On the Right hand side there is an option called as Parameters
4. Right Click and Select Add Parameters
5. at the right side there is an option called as Default Values
6. Choose "Specify Value"
7. Enter your desired value for this parameter and hit Ok
Thanks.....:-)