1) Make sure you have run vanilla Minecraft 1.7.10 at least once. If you haven't run it in your current install, make a new profile, and select Release 1.7.10 from the version dropdown menu. Download the Forge Installer for Forge 1.7.10. To do this, click 1.7 > 1.7.10 > All Downloads, and then select the installer for version 10.13.2.1300 (the newest versions of forge have trouble loading some of the mods we use, and this is the latest, tested build.). Some people, especially those using WinRAR, experience issues with executable jar files and need to download the Installer-Win instead. Double click the file, select "Install Client” and click Install.
2) Run the Minecraft launcher; select the newly created Forge profile from the dropdown menu in the bottom left hand corner of the launcher window. Login and press play. A Minecraft window will appear and Forge will be setup. When that is done and Minecraft appears, close it.
3) Navigate to your .minecraft folder. An easy way to do this on Windows is in run (xp & newer), or the start menu search bar (vista & newer) type %appdata% and press enter. On Mac go to Users->Library->Application Support->minecraft ("Snow Leopard" or older), or do Shift-Command-G in your finder and type in ~/Library/Application Support and press Go ("Lion" or newer). Open the .minecraft folder, and then move that window off to the side.
4) Download Mo Creatures 6.3.1 for 1.7.10 and Custom Mob Spawn 3.3.0 for 1.7.10 from MoCreatures.org/downloads. Put the Mo' Creatures and CMS zip files in your mods folder. Do not extract them! If you are on Mac and anything downloaded as a regular folder, look in your trash for the original zip archives.
5)Reopen Minecraft and make sure to run the Forge profile. You should now be able to connect to the SMP server. If you followed these instructions exactly and have issues, please start a thread in the Help & Support section of the forums. Include any crash reports and/or the forge log. Do NOT post stuff in the minichat or PM staff. You'll just be told to make a thread anyways.
6) These are optional, but we also recommend getting a minimap mod, such as Journey Map(but only the Fairplay edition) and Optifine Ultra for 1.7.10. Both go in the Mods folder just like Mo Creatures. We also HIGHLY recommend using our custom texture pack. The link is below. It is a modified version of the Faithful 32x pack by Vattic. Please support the official release.