snaphu.conf contains the command which you execute in the folder where you exported the phase. It converts it into an unwrapped phase and stores it into an img file. The corresponding header (hdr) is already generated at the export.
In Linux, you right-click in the folder where your exported files are, and select “open in command prompt” or something similar (depends a bit on the version).
Then you enter the command from the text file (you don’t need nano for that, just open it in any reader) and confirm with enter. If snaphu was installed correctly, a process for phase unwrapping is started and the img file is generated. You then import it back into snap using Radar > Interferometric > Unwrapping > Import using the instructions given here: Problem in Snaphu Import section
Please note that since snaphu v1.4.2 you don’t need ubuntu any longer and can run snaphu from Windows as well without any installation: http://step.esa.int/main/third-party-plugins-2/snaphu/