car wont work?

i was driving my car round my field (as im still a learner and havnt passed my test) and it was working fine no problems then the last time i was driving it i noticed there was a little battery warning light that lit up i didnt think anything of it and parked it left it tried to drive it the next day and it wont work at all even the key wont open the car unless i use it manually then if i turn the key in the ignition absolutely nothing happens please help!!