Van wont start

I have a 98 Ford E-350 with a V10 that ill not start.
i have replaced the starter and battery on it, when I turn the key it acts and sounds like a dead bettery.
does anyone have any Ideas what it could be??? and please in laymens terms tottaly mechanically inept.
thank you.

Clarify “acts and sounds like a dead battery.” This means different things to different people. Describe what you actually hear when you turn the key.

Did anyone put a voltmeter on the new battery to make sure it is charged? Don’t assume that it will have proper charge brand new off the shelf. In fact, most batteries sitting on the shelf will not be fully charged & it will be worse the longer they’ve sat there.

You should probably replace your main battery cables. At the very least inspect them - including underneath of the insulation - for corrosion.

Of course, depending on what the thing actually does when you turn the key this might have nothing to do with battery, cables, or starter. If its an automatic try starting it while its in neutral.

when you turn tyhe key it just makes the clicking sound like a dead battery. i have placed thebattery in my truck and it started right up. i have yet to actually check the battery cables so that will be my next step.

be sure and check all the grounds, cleaning both ends, and all the heavy power cable, cleaning both ends (or replacing the cables). With a proven battery, it has to be the connection, or the starter itself. You could remove the starter and get that tested…but I’d go with cables first.