what steps do I need to take to do a readiness monitor test for emmissions on 1996 Ford Explorer

I just purchaced the truck and the previous ouner just replaced the battery and never drove it after. I failed emmissions and the check engine is not on and the tech at the emmission place said that it says the readiness monitor is not ready and it may need to be driven. I just need to know what I need to do for this readiness test to say ready

Asked by for the 1996 Ford Explorer
Drive the thing for about 50 miles.