keyless fob
 

hi all new to here so i just got myself a 2.0 impreza sport estate 2001 x reg it came with one key no button and a fob with one button but no key (not broken just no key)need help changed the battery in the fob as it didnt work,thought was dead but still nothing is it for the central locking?? or is it an alarm fob lol not sure if even has alarm need help

thanks in advance :notworthy