Chat to a player/partner.

1. Press his/her (blue) Alias - at the table or on the members list so the Profile shows.
2. Press Chat To - left of the alias in the profile - this high-lights the chat out in yellow, and sets the chat to go to the selected player.
3. Type your chat - press Enter (or the blue arrow )
Note: If the player you're sending your chat to is seated at a table, then all players at that table will see the chat.

Press the X to turn OFF the 1-to-1 chat. 
Press  for more Chat Options.