The easiest way to open a locked car trunk would be to unlock it with your car keys! However if you cannot manage this or you have lost your car keys, then it might require a bit more effort and ingenuity to manage to get your car open. You should only be thinking about trying to open a locked car trunk if the car in question belongs to you. Trying to open someone else's car trunk without their permission would be illegal and is likely to get you into significant trouble with the police.
If you have access to the driver's seat of the car, then check to see if there is a trunk release button located somewhere inside the car. It is often located under the steering wheel or on the main console of the dashboard. If you know that the car has a trunk release button inside but you cannot get inside the car, then it will be easier to prise open the driver's side door and then use the button to open the trunk rather than trying to prise open the trunk first.
As long as you can get into the car, then there should be other ways to get the trunk open from the inside. If the back seats of the car fold down, then you should be able to crawl into the trunk space where there should be a trunk release latch that will release the trunk door from the inside.
If none of these options are possible, then the best course of action is probably to either call a locksmith or a car breakdown service, as professionals are likely to be able to prise the trunk open causing as little damage as possible to the car.
If you have access to the driver's seat of the car, then check to see if there is a trunk release button located somewhere inside the car. It is often located under the steering wheel or on the main console of the dashboard. If you know that the car has a trunk release button inside but you cannot get inside the car, then it will be easier to prise open the driver's side door and then use the button to open the trunk rather than trying to prise open the trunk first.
As long as you can get into the car, then there should be other ways to get the trunk open from the inside. If the back seats of the car fold down, then you should be able to crawl into the trunk space where there should be a trunk release latch that will release the trunk door from the inside.
If none of these options are possible, then the best course of action is probably to either call a locksmith or a car breakdown service, as professionals are likely to be able to prise the trunk open causing as little damage as possible to the car.