hello there!, im a noob at zb and i have just finished my first human body model. I plan to make an armor for it, how can i start it in zb?? 
There are a couple ways to get started.
Option One is to use Mesh Extract. You mask what you want to become armor, then press a button to create a new SubTool. The topology of the extracted object will be based on the original.
Option Two is to use Retopology and just design what you want. It takes more time, but gives you total control of the polygon structure for the new pieces.
Both are covered in the links in my signature.
thanks aurick! the mesh extraction helped a lot! but iām still confused about retopology. is there a step by step instructional about retopology?