Unless some fuses are blown, the car should start using a donor car with the engine running for power. If the battery is completely dead a "walmart" booster will not do it. Depends on the booster here...
If you hook the cables again while another car (recommended a pick-up truck) is charging for 15 minutes, and try again, you might be able to start it. Cables have to be thick, hard to bend, so the amperage can be transferred.
If you don't have any power when you get the cables from another car with the engine running, some fuses might be blown somewhere.
JOY = BMW