The software uses current locale of the user on the computer where it is installed. To make it available for all users, the software had to be installed using Run as Administrator in the first place. Once it's installed for all users, simply change the language and then close it. With the next user, run it samet way and the language will be the one you setup. Additionally, it is possible that the product doesn't support installation for all users.
As for the connection method, simply access the ProSet application and delete all the preferred networks and configuration. Configure the one you need, repeat the procedure you mentioned and it should work normally.