Reloading myfirst_niosii software project?

I am a newbie. I have successfully built the myfirst_niosii project with the hello_world_small software project. I was able to run the software on the newly built Nios II processor in my DE0-NANO Eval Board with Version 15 Quartus II - 64-bitWeb software on Windows 10.

When I returned to the project to extend the software, I was able to reload the Nios II processor, but was unable to open the software project. The "Open Project" button in "Nios II - Eclipse" is greyed out. How do I open the existing Project?