This video will show you how to download and install The Golden Cobblestone modpack, which can be found on the ATLauncher
Please be sure you use newest Java 8 64bit, and allocate atleast 4096mb ram at maximum memory. If you cant allocate that much you most likely wont be able to play the pack, or you use 32bit java, and need to get 64bit.
You can download Java 8 64bit from https://java.com/en/download/manual.jsp (Use the Windows Offline (64-bit) link if you use Windows)
Link to the pack: https://www.atlauncher.com/pack/TheGoldenCobblestone/