How can I get a replacement Panasonic KX-TGA1018 handset?
You can purchase them from the link below:http://www.amazon.com/Panasonic-Cordless-Accessory-Handset-KX-TGA101S/dp/B000LY8B3S/ref=pd_cp_e_0That's not the same model number that you referred to, but it's the replacement model. It will work with your phone system.Let me know if you still have any questions about it.
I don't understand what I am supposed to do?
You can just click that link, and then you can purchase the extra handset from there:http://www.amazon.com/Panasonic-Cordless-Accessory-Handset-KX-TGA101S/dp/B000LY8B3S/ref=pd_cp_e_0
Considering the price, I prefer to just buy a new phone set. Thank you for your time.