That's a good question---!
As with most cars, except some vintage vehicles, it goes like this.
Sit in drivers seat.
Ensure gearbox is in neutral
set handbrake
Pull out the choke
Turn ignition key to start while possibly opening throttle a little.
Release starter switch to run position.
Return choke when running steady.
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Before doing that, if the car has been standing for 15years, some preparation would be wise.
Drain fuel tank and flush out.
Strip and clean carburetters
Clean plugs
Renew engine oil and filter, cleaning sump and coarse filter.
Renew battery as the old one will probably be dead.
Be in a well ventilated area
Ensure fire extinguisher is serviced and ready for action.
Put fresh petrol in tank
Good luck