I have a new batt power seats work window wipers work and brake lights car won't start no lights on dash board no noise nothing 2001 deville radio went out so I turned the car off and when I went to turn it back on nothing car won't do anything I been told it was my anti theft system also been told about a main fuse I need some help please

See if this link helps:

https://www.askmehelpdesk.com/cars-t...ml#post2123675

When the battery was replaced, did the cables get inspected?
This car has a side-post battery. That style battery is notorious for leaking battery acid and causing massive corrosion, particularly on the Positive cable but could also damage the battery tray.
I would recommend that you disconnect the battery and inspect both Positive and Negative cable ends. Eye protection is also recommended.