Hi everyone, first post so please be gentle, i can i firstly say im rubbish with cars!

Went to get in the car the other day and realised the key fob wasn't working, so put a new battery in today, still not working. just tried the key in the lock and it opens fine (but im sure the alarm used to go off until i put the key in the ignition) but its only the one door that opens(drivers side). tried the key in the ignition and there's nothing, even the light that indicates the alarms on isn't blinking. my first instinct is that the battery has gone dead in the car but like i said....im rubbish with cars. any help would be greatly appreciated!!

*posted in the wrong section originally so sorry if you've seen this already*