1) buy the plants
2) plant the plants
3) water/weed every day
4) depending on the plants they may need special watering habits or fertilizers, and some need things to help the growth of the plant during the first year, make sure that all needs are met and that every plant is doing well.
you may need to research and individual plant. They are a little like animals, they need food and water every day but depending on the animal they may have special needs. Don't assume that buy doing steps 1-3 that your garden will do well, you need to know what you are growing and what it needs to do well.
If you have a veggi garden you will need to harvest, this also depends on the plant. They all produce at a different time of year.