How to get a value from a dll.....

my project is based on online tutorial.We r using a external kit (using MCP 2200 Micro controller).I have to get values from this kit to my project(to textbox).kit is connected by USB port.I got the dll of the kit. There r lot of keys in this kit just like a calculater. If I press a key(say 1) in the kit,the value(1) must be shown in textbox. The thing is I want to know how to use a dll in asp .net project. I added the dll by Reference and I got the methods used in the dll. Methods r working. But the thing is I don't know the actual process to get this output value from the kit to my textbox. I'm attaching my DLL PDF here.
i'm trying hard to get the output...