Punto old fiat R reg. ?

My hubby took battery off car and charged it it over night, the car started wen battery was put bk in then he switched it off and now it will not start the alarm goes off I need help pls as to what to do next we have all paper work and codes but do not have a clue in wgat to do. I want to get it working to sell on asap so if any one could help I'd b much appreciated thanks