As we know 20.1 is launched on 23rd april.
I tried to download it but i am using apex.oracle.com for learning. How do i upgrade that to 20.1?
I downloaded the 20.1 set up but cannot understand how to install/upgrade?
If I correctly understood the question, you'd want to upgrade Apex version which you use on apex.oracle.com.
If that's so, no - you can't do that. Oracle guys will do it when they find appropriate. Usually there's a notice on that site about "scheduled maintenance" or something like that.