Make sure to start with the basics of the engine -> take a look at the starter tutorials that you can find on the official youtube channel. After that directly start creating your things -> when you have questions, just post them here into the forum - we are always here to help 
Some very useful links (many good information + tutorials):
https://wiki.unrealengine/Main_Page
https://docs.unrealengine/latest/INT/
https://wiki.unrealengine/Videos
+take a look at the free samples from the learn tab