Are you using this application in a Cloud Provider (AWS, Google, Azure, ...), in the native installer (Windows, Linux, OS X) or in a VM?
In the following links you can find the information on how to use putty according to your type of installation:
- Cloud Provider
- Virtual Machine
- Native installer In this case, we do not provide any specific settings. You must use the user and the system key (Ubuntu credentials in your case), not the stack or the application itself.
Carlos R. Hernández