What part of the board is getting hot?
What do you have connected to it?
Photos?
Have you gone through this guide?
https://docs.duet3d.com/en/How_to_guides/Getting_connected/Getting_connected_to_your_Duet
Or perhaps this one?
https://docs.duet3d.com/en/User_manual/Troubleshooting/Duet_wont_respond
When and where did you purchase your Duet?