Trouble installing erpnext into my second frappe site

Hi all.
I’m trying to set up a second erpnext installation on a debian 8.2 virtual machine.
I followed the easy setup script for the first site and it’s working wellso far.
I tried to set up a second site by following the instructions at

I’m using ports to differentiate between the sites. All went fairly well until I logged into the second site. I don’t have erpnext itself installed, it seems to just be the frappe framework.
I tried running
bench install-app erpnext
I don’t get any response to that command and nothing installed.
I tried
bench install-app erpnext “sitename”
But get an error about an unexpected argument in the command.
I think i’m missing something simple but not sure what.

Help?

command for installing on non default site is

$ bench --site "sitename" install-app erpnext

Thanks.
I believe this will work. Tried running the command just now but it’s telling me I have to clean up the site first.
I’ll try and figure that out in a bit, don’t have time now.