My child units have been asking me to install the Galacticraft Minecraft mod for many months. While we have lived in Minecraft for 3+ years, I had never installed any mods and had no idea how to. So I started reading.

The Galacticraft wiki and forums have a lot of info, but skip a few steps that are probably obvious to non-noobs.  So here is a step-by-step guide to installing both Galacticraft server and client for Minecraft mod noobs like myself.

First the server. We run multiple worlds (listening on different ports) on an iMac running OS X 10.10. All worlds use Minecraft 1.8.7.

1. Start with a new world because an existing world will not have the necessary ores. Just make a new, empty directory.
2. Download the latest Forge.
3. Download Galacticraft for 1.7.10. 1.8.x fails to run because it cannot find the CPW package.
4. Run the Forge installer. Select server. This downloads Minecraft 1.7.10.
5. Make the mods directory and move all of the Galacticraft jars into it.
6. Modify the startup script to call the Forge jar instead of the Minecraft jar.
7. Edit server.properties. Change the MOTD. Optionally change gamemode to creative to make the game more playable for younger players.
8. Run the startup script.

Then the client. The kids run Minecraft on Windows 8.1 machines.

1. Make a backup of ${appdata}/.minecraft.
2. Download Forge. Beware of deceptive ads on the download page.
3. Download Galacticraft.
4. Run the Forge installer. Select client.
5. Make the mod directory and move all of the Galacticraft jars into it.
6. Launch Minecraft and select the Forge profile.
7. Select multiplayer. Add a new server with the correct IP:port.
8. Open the Galaticraft wiki on a second device for easy reference.
9. Join the world.