You can support fellow Order members economically or militarily by sending reinforcements or carts of resources to their Towns. You can exchange messages with all members of your Order, so it’s easy to find out if anybody needs your help. All of these actions are available in the Order menu, Membership tab.

Click on the block with the player’s name and userpic, and select the action you want to perform in the window that appears:

The higher the level of the Port, the faster carts of resources will move.