Create your SSRS Report. Create a Statics Parameter by Right clicking on the Parameters Tab on Right as shown below.
Create a dataset for the above created parameter. you need to use the values of this dataset for parameter.
Select Distinct CountryName from dbo.Country
In this examples I am selecting Distinct CountryName from Dbo.Country Table.
Go to parameter Myparam which you have created and pass the values as shown in Fig
Create main dataset for your query those filed you will be using in Tablix. and configure as shown below. As we want to Filter the records depending upon Parameter value, Go to filter , Select the filed which should be used against parameter value for filter and configure as shown and Press OK at the end.