How to update unreal

Sorry for this post as it is probably retarded and in the wrong forum but I could not find anywhere for general questions. I cant seem to find any info on the most obvious thing in the world.

I have the unreal engine and a project ive been working on with 4.8.3. I downloaded some assets from the marketplace I would like to use. None of them work as they all say I need 4.9 or 4.10 How do I update?!?!?!?!

I have tried to hit get unreal again on the site but iot just reinstalls the launcher. I have tried clicking on the arrow beside Launch and Unreal engine 4.8.3 but nothing shows up?? How do I get the latest version???

In the launcher, there’s a + button to add installations of different Unreal Engine versions