We need way more information. How does the oil look? How did it run before you parked it last? Any dash lights on?
Put multimeter leads from the + to the - terminal on the battery. Have somebody crank it over for you. Watch the voltage. Does it drop severely? Ive seen batteries that read a solid 12 volts when sitting, and then you try to crank and the battery voltage drops straight to zero. It could be that