Step 1: Download the Launcher from this site. Choose appropriate OS. Once installed, put installer in its own folder (wherever) and name said folder ATLauncher. Run ATLauncher.exe
http://www.atlauncher.com/pack/YogscastCompletePack/




Step 2: Click the "Account" Tab and enter in your minecraft login information. Cannot download instances until this is done!




Step 3: Click on the "Packs" Tab then look for the Yogcast Complete Mod. It should be the first one. Then, click New Instance and continue until you reach the stage in the next step.



Step 4: This part is important. Click the "Select Recommended" option first, then "Install".



Step 5: Once its done, select the "Instances" tab. It should show the now completed modpack. Click play and come join the server @ minecraft.n00bfest.com:25566