My battery will not hold a charge. Replaced battery and alternator and still can not get my van to start. Getting a jump from another vehicle doesn't even get me two blocks

IF, in fact , you have a good alternator AND you have charged the battery with a charger(NOT another vehicle) , the next step would be to start checking and TESTING the wiring and find the 'open' that I suspect is causing the 'no-charge' situation. Have you checked/tested ALL fuses?