Make sure the battery is fully charged. If it is, test the starter solenoid by shorting the two large electrical post with a screwdriver. If the motor turns over, then the solenoid could be bad already. If it does not turn over after shorting the solenoid, make sure the battery terminals are clean and tight on both ends and also the red cable connected to the starter. If all connections are clean and tight and battery is fully charged and shorting the solenoid does not crank over the motor, the starter could be bad or needs some disassembly and cleaning.