There are two types of flange repair kits but the flange is in fact glued to the pipe.
Kit number one consists of two metal bars, Curved, depending on the kit they may "Join" to form a circle or they may be quarter circles each.
These 'Slip' in under the remaining portion of the flange and allow you to lock down onto it.. IF you have the broken off pieces I'd glue 'em on to make it look nicer but the metal acts like a big washer bolting the toilet down to the rest of the flange.
The other one fits inside the existion flange but you will have to chip away part of the flange to use one of those. (Or cut it off)
You cut where it flares out so the "Flat" part is tossed and only the bottom part remains. the 'Expand a coupler" goes into the pipe (The part the flange is glued to) and you twist to expand the washer and lock it in, you will then need to attach the flange to the floor and the toilet to the flange. NOTE: Last saw one of these about 2,000, have not looked for one since.