Implementing extra line in entry form (What Im Lis

Ive looked through all the php forms I could think of that would have somehtign to do with adding an extra entry field on the posting page but I can’t make heads or tails of it. How would I go aobut adding an extra text entry field (or maybe somehow bracketing a line in my post so that it will be seperated) so that what I type appears below the main entry with somehting like Currently Listenign To: or Mood: next to it?