so try this :
create a new project C# for example
in solution explorer window you can see your project ;
Right click on your project and click > Add reference...
select the brows tab in reference window ,so here you can select your
*.dll file and add it to your ref.ok?
now you how you wanna use that :
in your form code behind(you can Rclick your form and select view code or
click on your form design (Form1.cs[Design]) and press f7).
you must instance your class like this:
mydllclass ob=new mydllclass();
ob.
:thumbsup: