How to invite my facebook (and other social network) friends ?

No problems about your English. You're doing fine

To use the Requests feature, first you must have your Canvas URL working. For that, you need an SSL Certificate on your site. If you have that, then Autotune should setup your Canvas URL for you. The Canvas area is a way to show your site within Facebook, like:
apps.facebook.com/joomla-extensions/

Once your Canvas is setup, you need to create the Request in the Requests admin area of JFBConnect. Then, you can add that Request to any page using the JFBCRequest module or JFBCRequest tag. All you need to know is the ID of the Request you created. For the full guide on Requests, see:
www.sourcecoast.com/jfbconnect/docs/facebook-requests

Hope that helps,
Alex

Glad to hear it! If you need anything else, just let us know!

Alex