1. Download Minecraft Forge: http://files.minecraftforge.net/minecraftforge/minecraftforge-universal-1.5.2-7.8.0.684.zip
2. Install Minecraft Forge. (If you do not know how, look at this video: http://www.youtube.com/watch?v=b0b2u8cdUSs)
3. Run Minecraft so that Forge installs.
4. Download the mods needed to join the server: http://puu.sh/31hFI.zip
5. Put all of the zips (Do not extract them!) into the "mods" folder of your .minecraft directory. (It should look like this: http://puu.sh/31khz.png when you're done)
6. Join the server!

List of mods: (Read all about 'em!)

Weapons Mod: http://www.minecraftforum.net/topic/211517-152forge-balkons-weaponmod-v111/

Spawn Zombies: http://www.minecraftforum.net/topic/1553186-152forgemodloader-mob-spawn-controls-control-spawning-increase-spawncaps-spawn-attempts-mocreaturesextrabiomes-support-updated/

Zombie AI: http://www.coros.us/mods/zombieawareness

Rei's Minimap: http://www.minecraftforum.net/topic/482147-152-may10-reis-minimap-v33-06/page__p__6349298#entry6349298