how can i fix my sigma SG10E?

Recently my battrery went dead so i replaced it,the problem i am now faced with is every time i go to start my car the siren goes off, lights begin to flash and i cant start her up. I only have immobilizer fob(m36t meta immoiliser)and no alarm fob (sigma sg10e) was supplied with the car, please help, what can i do!

Mitchal