Ah, the bone key...
Many people during my time sought it out for bragging rights. I have one that I still use today. It's actually really simple. If you have any flying mount or wings, make a small arena of platforms and run around in a circle while taking shots at it with a sword that shoots a projectile or a gun of any kind. If you have no ranged weapons, it will be a lot harder. If you only have swords, follow these directions:
First of all, make the arena almost 3 times larger. This will improve your ability to survive greatly, as it allows you to run left and right and jump up and down to evade the guardian. Next, take the longest sword you have (If you've defeated the wall of flesh, the Breaker Blade is recommended. It has the longest reach of all melee weapons. Damage does not matter, as any attack only deals 1 damage to the Guardian other than criticals, which do 2 damage. Thus it is recommended you use a large, but fast sword to do damage quickly. The ideal armor is Titanium armor, since it allows you to dodge an attack every 20 seconds. Don't attempt anything with a sword until you have titanium armor. Just evade the guardian for 20 seconds, start swinging and pass through it once, and ONLY once so it registers the buff of the titanium armor and successfully dodges the attack. Hit it as many times as you can in that short period of time.
I hope this helps. Leave a message on my talk page if you have any questions.
If you want access to the dungeon, Skeletron is much easier.
Why do you aim to defeat the Dungeon Guardian?
I do not understand the meaning of your message.
I would give you a good weapon, but I don't think computer can cross-play.
If you have an automatic weapon such as the Megashark, use it with chlorophyte bullets to increase the amount of ammunition that actually hits Skeletron Prime. If you don't want to waste ammo, try this: First, place all your coins in a chest or storage space somewhere. This requires a full set of turtle armor, so put that on. If you are on mediumcore, put everything you don't need into a chest, grab it later. If you are on hardcore, DO NOT DO THIS. Now, once you're ready, head over and summon skeletron prime. Evade it, and do not worry about damaging it as that will come later. When it is dusk it will rush at you and deal 9999 damage, which is an instant kill for player characters. But, since the Turtle armor set has so much thorns effect it deals 9999 damage to skeletron prime as well, and you both die. All you need to do is travel back to the place where you died, and pick up your loot. Easy as said.