There is a dialog box named Add reference, this is basically used to add a reference or to delete a reference. And this is available under project menu. Following is the steps to add reference in c#.
2) From the project menu, select Add reference.
3) Then an Add reference dialog box will open.
4) Then select your reference or browser from browse option
5) Then click ok.
And finally your reference is added in project.
Reference post:How to: Add and Remove References in Visual Studio (C#, J#)