why does isnt my battery charging. Have new alternator and batt. on 1991 Mazda Protege

I have replaced the alternator and the battery.the battery has been replaced twice within the last two days.

Asked by for the 1991 Mazda Protege
Check the 80 Amp "Main Fuse" large blk/wht wire at Alternator should have Battery voltage all the time,as should wht/red, black wire is ground, smaller white/black goes to the dash warning light to turn it off when the alternator starts charging.
thanks. i'm a try it out now.