C# working with sql server 2008 r2

Question

I have a C#.net 2010 web form application that I need to add two tables to the database. This application uses linq to sql. Can you tell me if I want to add these two new tables to the sql server 2008 r2 database, do I

1. Need to remove the original .dbml file and recreate the .dbml file?

2. I would think I can just add two tables to the database and somehow refresh the existing .dbml file. If this possible?

Whatever your answer is to the question, can you tell me how to solve this problem?