localhost install of site, plugin installation and login issues

I wanted to start using the plugins and themes locally while I wait for my nameservers to propagate changes his weekend, but it seems an error is thrown if I use localhost. I've included a screenshot of the error message. How do I use any of the plugins or themes locally? I can't log into my account locally so far, so I'm not sure how to continue.

https://www.dropbox.com/s/qw5gz7ghotuys4n/Screenshot%202016-09-04%2003.53.20.png?dl=0