Adding doors

Hello,  I have a home that when you walk in there is a formal living room to the left and then off that is the dining room... in one of the open frames, I am wanting to add double French doors. the space is 60x80 and my friend is actually giving me her double doors she doesn\'t want any more and they measure 29.75x80. My question is, the frame area isn\'t meant for doors... how can I put two doors up on the existing casing without having to rip it off and get something new... I hope this makes sense... there are no cutouts for hinges or any kind of raised area to hold the door.. I really hope this makes sense... Thank you in advance