You might need to add a "using" statement for C#, or an "imports" statement to the top of the file to bring the object into scope.
When you add the reference, it asks you for a name. The default name for the reference to a local site is "localhost". If you used the default, you will need to add one of the following lines.
using localhost; //C#
Imports localhost '
VB
That will bring the object into scope so that your code will compile. I believe that the instructions probably gave you a name to use such as "ReportingService" or something like that. What ever you used, you will need to modify the directive appropriately.