C# create new linq to sql file problem

In a C# 2010 web form application, I created a new linq to sql (*.dbml) file. When this occurred, the .net framework created a default connection string. However I want the *.dml file to use the connection string I specify.

to solve this problem, I have the following questions:

1. When I do create a new .dbml file, how to I make the .net framework use the connection string I want to use and not come up with a default connection string?

2. For an existing .dbml file that I added to the application, how can I change the default connection string to the value I really want to be used?