Hey ,
Here is a great [forum post][1] for you to learn how to install the Engine. Simply open up the Epic Games Launcher, click on the ‘Library’ tab and then click on ‘add versions’ that’s towards the top. You can then select which version of the Engine you wish to install. The latest version that’s out is: 4.8.0 Preview 2
Let us know if you have any further questions, thanks!