Fresh pineapples tend not to have seeds or not fertile ones as they are hybridised to be seedless and also are picked when green before any seed has developed. Most of the propagation of pineapples is now vegetative by offsets or the tops. The easiest way by far is to take the pineapple top, cut off with half an inch or so of the flesh, allow to dry for a day or two, or then plant in sandy compost, with bottom heat. Put a polythene bag around the pot, and keep an eye on it to check the top isn't rotting. With luck it will start to root after a month.
If you keep it growing on in a sunny frost free place, and pot it into a VERY big pot, you may be rewarded with your own pineapple after a couple of years.
If you are lucky enough to really have a fruit with ripe seeds, they will be in the lower part of the fruit, and should be sown fresh in temperatures around 80F. It would be fascinating to do this, bearing in mind they are a bromeliad and would need similar treatment in growing.