... okay... you gotta speak the terms if you want the help.
A phone LINE is the hardware that is connected to a phone number. Call a line, the phones connected to that line ring. More than one line = more than one phone number. You can have one phone conversation per line.
A PHONE is simply the piece of equipment that you talk on... if you call it a line, it will ring. If there are different phones connected to the same line, they will all ring.
Now... are you just wanting another phone so you don't have to walk to the bedroom to answer it, or do want a seperate phone number for your office?
If you want another phone... there are many multi-handset phones, where you have one base station and the others connect wirelessly. You just have chargers for all of them and can put them in whatever room you want. (Easiest and affordable choice)
If you want another line, you'll need the tech anyway. Get it done right and save yourself the frustration.