you didn't say if petol or diesel,
first thing is to clean all your high tension leads to spark plugs,any dampness will short out the leads and plugs, and clean around your battery terminals, 9 out of 10 ,dampness is the main cause ,.
Get your battery fully charged
if its diesel, then get your glow plugs checked, just one not working could stop it from firing over.
while your battery is being charged, do your oil and water checks.
if the car still don't start, then you will then need to check your spark plugs, they might need gapping or replacing
its worth buying a battery charger, preferably one with a gauge, and charging at home,it takes a about 5 hours