just right click on the Solution and add new Project, one New window is pop up "Add New Project"then select Windows and you can see in the center window have many option are there, select a class Library and then click ok.
new project will be add in Solution. you can seen four option like classLibrary1,Properties,Reference and your class Name Class1. Add you data in class as you want and Build this project,simple copy the DLL path, if you can't get a DLL path just Go View Option and select output. I hope output is showing. Build again your project output is showing this type of Path,This is Different path your side
E:\myspce2\c# program\LAB MASTER\myclass\bin\Debug\myclass.dll
copy this path and add in Reference Project, you can used the Class. I know my english is worst but i try best. hit to reply for more information
Happy Cooding ☺