I think this was already addressed, but here are the instructions again.
- Connect the controller to your Formuler device with the USB cable.
- From the Market, download and install the Game Controller Test app.
- The controller should be recognized and the buttons you press on the controller should be shown visually on-screen.
- Now you have verified the controller is connected and working.
You asked how to connect the controller to the device and the method has been presented to you.
If it is not working with 3rd party apps, you may need to remap the buttons to something that particular app can recognize.
Don't ask me how to do this because I don't know. Try Googling the solution, maybe some information is out there.
If you can't be bothered to do some research on your own, the controller listed below works out-of-the-box with many 3rd party emus: