there are 2 ways. i'll explain both ways in details.
Method 1 (the easy way):
step 1. Kill mobs
step 2. Go to
http://www.three-dimensions.com/rh
step 3. Kill more mobs and save up your money
step 4. give me your money and i will give you a mitrill cuirass
step 5. Send a tell saying "thanks, nice doing business with you"
Methodd 2 (the hardway):
step 1. buy mining picks (from shops or from people)
step 2. find the mine in Midian
step 3. mine for copper
step 4. process your copper into bronze at a forge
step 5. type craft with bronze in hand or portal
step 6. follow direction
step 7. when you successfully made one, store it someplace safe.
step 8. repeat step 1 and 2
step 9. mine down to around 550ft (make sure you add the pillar)
step 10. mine for mitrill
step 11. process mitrill ores into mitrill ingots
step 12. have your cuirass in your inventory and the mitrill
step 13. type reforge cuirass mitrill
of course, you can always type "help craft"