1. If your using LINQ , i think you also use "LINQ to SQL" class for mapping. then drag drop your tables and SP in "LINQ to SQL".
private TenderManagementDataContext __dataConnection = null;
__dataConnection = new TenderManagementDataContext();
__dataConnection.AddSiteUser(emailID, username, password);
2. Create object of "LINQ to SQL" class where you want to call SP.
3. Then call your SP with paramaters.