You've made it, it's the final stage of Mega Man 4!
The stage is so simplistic and straightforward it doesn't even merit a walkthrough. Just remember this - you need FULL PHARAOH SHOT POWER before going into the final battle. This is REQUIRED to win the fight with Wily! If you need to replenish your weapon energy, kill yourself and continue.
Boss: Wily Capsule
You find yourself in a dark room, with Wily appearing and disappearing. You need to hit him with a FULLY CHARGED Pharaoh Shot - NOTHING else does damage. Fire the shot the second he appears on the screen, and you should be able to hit him before he disappears (he won't technically "disappear" until a few seconds after you see him leave the screen, so you should still be able to hit him even when the screen goes black after his brief appearance.
A tip for winning the fight. You can hit Wily with the charged Pharaoh Shot hovering over your head, and he'll take damage - but when you let the attack button go, you'll STILL fire a fully-charged Pharaoh shot! And it doesn't use up any additional energy, either! A very useful strategy that can allow you to conserve your weapon energy in this, the ultimate battle.
Congratulations, you've beaten Mega Man 4!