How to set unity for finding the c# dll?

Now I have built a c# library called ClassLibrary.dll and want use its function in my unity's c# code. As we known,in order to achieve the goal, we can add path and reference in the IDE vs2005. I am puzzled how can I do that in the unity?

Thanks for your help.

You can simply include the DLL in your Assets/ folder. Unity will automatically pick it up.