Pro-site install

Hello,

I can't find the instructions to install the Pro Sites plugin.

Where could I found them? There is a file inside the plugin? Where?

I already downloaded the folder, and uploaded into the /plugins directory, I tried to activated and is giving me this error message:

Fatal error: Call to undefined function switch_to_blog() in /home/fjpyme/public_html/wp-content/plugins/pro-sites/pro-sites.php on line 194

Thanks,
Fran.