error when install the plugin!

When i install the plugin i get this message “The plugin generated 709 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.” have only install nex no other plugins are install.

can make a form an save it, but the next problem is when i make a page an click on the icon to insert the form, i only get a white popup box no option to choice-