How to include custom values in dropdown

Question

Hi,
  Now i need my project for adding cusomt values in dropdown. meantime. I had dropdown named biodata, its consists of age, gender,sex, religion. Now i need add item name custom for users chooses its from dropdown another pop-up will appear, and it had form and they filled it up thier details respectively.
Anyone could known pls help me.
Advance in Thanks
H.AL-MUBARAK