Use of DLL file in creating a class library

1)u need to build the first classLibrary1 then u will get the that DLL file in the same path (check in debug folder )
2)next in the classLibrary2 application inthat goto add reference u need to add(ClassLibrary1.dll) here

then u will get the classLibrary1 methods in the classLibrary2.................

Please refer:
Creating C# Class Library (DLL) Using Visual Studio .NET[^]

Walkthrough: Creating and Using a Dynamic Link Library [^]
In this walkthrough, you will create a dynamic link library (DLL) containing useful routines that can be used by other applications. Using DLLs is a great way to reuse code. Rather than re-implementing these routines in every program you create, you write them once and reference them from applications that need the functionality.

Also refer:
How to: Create and Use C# DLLs (C# Programming Guide)[^]

Click on add Reference then browse the location then do all u need

Yes . Just add reference to the first class library in the second class library.