2002 Dodge Stratus Recently Bought R T Replaced Battery Car Cuz Shot Had Key

i recently bought a 2002 dodge stratus r/t. i replaced the battery in the car cuz it was shot. when i bought the car all he had was the key, said the fob was lost. when i go to put the battery terminals on,the car alarm turns on and blairs i tried turning the ignition on and waiting. ive tried pulln the terminals off and the fuses and reseting it that way but no luck. can you please help me or do i need to somehow get a new fob for this car????? also there is no information that has been helpful so can you take me step by step what to do???