Fiber Phone Jacks in Multiple Rooms

Depending on your current wiring you may be able to use your homes existing wiring by feeding it from the modems phone jack. Make sure to isolate it from the incoming old feed to prevent damage to the modem. Otherwise, same principle only you'd have to wire it from the modem to a distribution point if more than one jack is needed. 

Thank you for responding!  We had to replace our Mom’s home, so there is no existing wiring. 
I am not sure if we need to run the new wiring from the outside box to add the jack in her bedroom or if we splice it from the inside somehow. 

She cannot see well, so cordless phones just do not work. We have the big button corded phone in the living room and really need to add one to the bedroom. 
I appreciate any advice!  

If you have digital service where the phone service if feed from the back of a modem that's where it needs to be terminated. You can use a Y adaptor if you need an extra connection. best way would be to go from the phone jack to a distribution point somewhere. If there's only going to be the one location you can go straight to the modem.