Ueno Station is a terminal station where Keisei Skyliner directly takes you from Narita Airport. (Accurately, Keisei Skyliner takes you to Keisei Ueno Station. So, you need to walk to change the train for JR line or Tokyo Metro.) Yamanote line, Ginza subway line, Tohoku Shinkansen, Joetsu Shinkansen and more stop at this station.
Surrounding Facilities
Ueno is famous as
Ameyoko

Museums


Zoo

And shrines and temples

By the way, above museums and zoo are closed on Monday. I shouldn’t have visited there on Monday 🙁
Change the train at JR Ueno Station
Changing the train at JR Ueno Station is a little confusing if you are not used to. At least, I didn’t know where I should go to reach to a correct direction at first.
Suppose Yamanote Line platform is on 1st floor.
Park Exit (Exit for Ueno Park, the museums and the zoo) is on 2nd floor.

Central Gate, Shinobazu Exit, Hirokoji Exit are on 1st basement floor.

And then, if you get on a subway, you go to underground after going through Central Gate.
Besides, you need to pay attention to go to Shinkansen from JR local lines. If you go for a passage for Park Exit (in other words, to the 2nd floor), you can NOT reach to Shinkansen transfer.
… I hope you understand what I want to say.

Briefly,
2nd floor: Park Exit near from Ueno Park
1st floor : Local lines platform
1st basement floor : Central Gate, Shinobazu Exit, Hirokoji Exit, Shinkansen Transfer
To get on a subway, you need to go down more after passing through Central Exit.
For your information, Central Gate on 1st basement floor is better than Park Exit to take Keisei Line or a subway, as the gate is near from each transfer location.


I wondered why the structure is so complicated. I suppose the reason is because JR Ueno station are standing at a middle of a hill. The park is on the top of the hill, on the other hand, Ameyoko and Keisei Ueno Station are under the hill. That is why, the structure seems to be complicated.

I usually change the train at Tokyo Station or Shinagawa Station. (Their structures are simpler than Ueno station). So, changing trains at Ueno station made me confuse. I guess it is not a big deal if I used to.
I am very happy if this article helps you.
Source of Map: JR-EAST: Guide Maps for Major Stations (Ueno Station)
http://www.jreast.co.jp/e/stations/e204.html