You get 4 butter blocks (gold blocks) and 14 cobble stone and what you do is you place the cobble stone like a x
Then in the spaces you put your butter blocks (gold blocks) there. After that in the very middle of where the cobble stone is put the core down. Once you have done that you put cobble stone on the core and make another x. When that's done put cobble stone on each butter block (gold block) then you are done then all you need to do is tap on the core and it will take you to the nether but if you are in multiplayer all players have to be close to the reactor.