Here is a visual guide on how to enable server resource packs for the Minecraft Middle-Earth server.

Step One: Open up Minecraft and click on 'Multiplayer' to bring up your list of servers.
Step Two: Then click on the Minecraft Middle-Earth server, so the edit option is lit up.
Step Three: Click on the edit option, your screen should look like this. Look at the 'Server Resource Packs' option next.
Step Four: Click on the 'Server Resource Packs' option until it says 'Enabled' and then click done to save your changes. Now you should be able to run the command in game to change the resource packs in Themebuild, Freebuild and Build world.

You can run the command by typing /rp {region letter} into chat. The regions are: e = Eriador, d = Dwarven, l = Lothlorien, r = Rohan, g = Gondor and m = Mordor.

Here's a very helpful guide to what warps have what resource pack by Lady_of_Rohan