car wont start?

If someone could help i would really appreciate ie. bought a 97 renault megane coupe with head gasket gone but the seller also said the battery was dead so i tried to jump start it but it wouldent start, with closer inspection noticed that the wireing for the alarm had been cut, now i have removed the alarm but the car still wont start and there is a light flashing in the dash its a little square with a squiggly line going through it. any help would be greatly appreciated.