The diplomacy page is a vital instrument for every alliance. The first set of options will allow you to send a NAP (non-aggression pact), confederacy or declaration of war to another alliance. Prior to selecting a diplomatic offer, you need to enter the name of the alliance you are sending the offer to.
Beneath these options, you will see a list of offers you have sent which are waiting for diplomatic action (an acceptation or refusal) from another alliance. Similarly, the next list will give you information about foreign offers (offers sent to your alliance from other alliances) including the possibility to accept or refuse them.
Finally, the last list will show you all of the existing diplomatic relationships of your alliance. These include: wars, NAPs and confederations.