If the starter draws more current than the charger can put out you may smoke the charger. It's better to have the battery connected to the car then connect the charger to the battery and try to start it.
Make sure the battery has water in each cell, enough to cover the plates inside. Use distilled water if it's low.
Charge the battery first for at least a few hours, Red to Plus and Black to Negative. Then check the battery voltage with a meter and a load (like a headlight bulb). If the battery won't seem to hold a charge a local battery shop can double check it for you. The battery may or may not be any good, if not you'll need to replace it.
There are 3 main battery and starter cables with 6 large bolted connections. If there are any poor connections or corrosion or paint on those terminals that can prevent the starter from turning the engine over.
Do not assume the connections are good, double check them all.
Does the starter solenoid 'CLICK' when you turn the key to the 'Start' position with the charger connected? If it doesn't, there may be additional problems.
If the car has an automatic transmission, one possibility is the circuit for the Neutral Safety Switch. If it isn't connecting properly the starter solenoid will not be energized.
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