To just post directly from Lightroom to Facebook use this plugin: http://regex.info/blog/lightroom-goodies/facebook
To have more sophisticated control you will need to setup Lightroom's Publish Services. Lightroom Help | Post photos online using publish services
Thank you very much for your help. I'm beginner with LR, so this looks complicated to me. I will see what I can do.
I did it!! Thank you very much.