Step 1: Forge
Have you found your adamantite yet? If you did you can craft stuff with it in an adamantite forge. To craft that you will need 30 adamantite ore and a hell forge.
Step 2: Forge Pt.2
To find those materials you have to go to hell again and find an oven. That is a hell forge. They are very common. And you probably already have the adamantite. Then you have to craft it in a mithryl anvil. And I'm probably spelling mithryl rong.
Step 3: Last
You can craft bars with it. Oh yeah, all of those pictures are of me. I look like a dragon!