First, make sure you and your friends are logged in to Facebook. 

Then, scroll to the left and tap "Play with friends". Tap “Invite” to invite your friends to play and click "Play". 

Select who you wish to play with and tap "Invite." The green icon next to the name of your friend indicates they are available to play. When the icon is red, it means that your friend is already in a game. 

When you have sent your invitation(s), all you have to do is wait for your friends. Each player can invite additional friends by tapping the "Invite" button. 

When you send an invitation, your friends will receive a Facebook notification and will see an icon indicating that you have invited them to play a game. 

In order to join your game, they simply need to click on the icon (the same for yourself if you receive an invitation from a friend). Once everyone has joined the table, click “GO” to start the game!