Plugin install - change FTP details

Hi team,
I have just installed the dashboard onto this site and would like to install other WPMU Dev plugins through that interface. The first plugin I clicked on asked me for FTP details, but was auto-filled so I assumed it had the correct details already and pressed OK. However, these details were incorrect and subsequent plugin install attempts always display the error "unable to connect to the filesystem. please confirm your credentials" but there is no info on where to do this. I have looked in the WP Config.php file, logged out and in again, and can't find any details through a google search. Where do I go to change the FTP details for plugin installs?

The updates page on Wordpress indicates I am up to date with Wordpress + plugins.