Buy celery and cut off the butt end and save. If you can't plant it right away, put it in a dish of water so that water is on the bottom part of the celery.
Once the temperatures outside are consistently above 50F, you can plant your celery into your garden. Remember that celery is very temperature sensitive, so don’t plant it out too early or you will kill or weaken the celery plant.
Just part the soil and plant in the ground as you would a bulb stalk side up. Lightly cover with soil and water.
Unless you live in a location that is ideal to grow celery plants, you are best planting your celery where it will get 6 hours of sun, but preferably somewhere that the celery plant will be shaded for the hottest part of the day.
Also, make sure that where you will be growing celery has rich soil. Celery needs lots of nutrients to grow well.