To initiate diplomacy, click on the leader you wish to contact in the upper right portion of the screen. The Diplomacy Panel will appear, displaying all known civilizations. Click on any leader to speak with them. Alternatively, you can click on a civilization's city banner to open communications with them.

When you engage in diplomacy with civilizations, you will have a number of options available, depending on your current relationship. This screen will also provide important information about your relationship, as well as the latest gossip about what that leader has been doing.

You may choose to declare war, or denounce the leader. You may also negotiate a trade deal, or demand stuff from another civilization. You can also propose friendship, defensive pacts, and send delegations.