It could be a number of things. First check your battery for corrosion and test if to make sure it holds a charge. Second I would say just unbolt the starter and test it. Those are the most common two problems to why a vehicle wont start. If its neither the battery or starter check the altenator.
do you have gas in the tank
How to install a battery?
wont start
Start with replacing the fuel filter.
How low is your gas tank ?
1997 fordexpedition wont start and the theft light is flashing
change fuel pump
needs a ignition cylinder and has to be reprogramed.
It may be the key, if you had one made it may not be electronic.
You need to charge your battery or get a jump. Replace the battery or have it checked because it is dead.
Then turn it off after it is put into park
Put gas in it.