I had this error that “could not download installation information code 1”, so i downloaded source code from github but i don’t know where to extract it from.
That’s how you use the engine from github: ?v=usjlNHPn-jo 
For the error: https://answers.unrealengine/questions/210207/cant-download-installation-informationtry-again-la.html
thanks for the video but the UI of github changed and there are no files to download, as the video shows.There is only source code and nothing else.
Well GitHub is where the source is hosted, not the installation. If you want to use github you clone the repository to your PC and build UE4 yourself.
Like this:
Open a Command Prompt with git and execute:
mkdir C:\UE
cd C:\UE
git clone git@github:EpicGames/UnrealEngine.git -b 4.8 4.8
cd 4.8
setup
generateprojectfiles
Open UE4.sln with Visual Studio 2013 and build “DevelopmentEditor - Win64”
You can also just download the .zip file instead of using/cloning github on your pc -> right side of the screen under “clone to desktop”
Also make sure that you post your error on answerhub: https://answers.unrealengine/index.html