Making your own custom workflow developed in sharepoint designer 2010

See more:

SharePoint

Hi,

I have a custom workflow(sequential), developed using Visual Studio 2010.
Now, I want to make it available to sharepoiint designer 2010 as an action. Has anyone done something like this before?

I have tried creating an action file and made changes in web.config, but when I open my designer it says it cannot find the assembly(my custom worklow).
What does it mean? I have tried this method by watching solutions on internet.

If anyone has done this task, kindly guide me.
Thanks a lot. :)