You can skip this and buy grinded/ground coffee, but we recommend you to buy the grind in small pack and finish them fast! (in 2 weeks, sometimes I do 1 month). Seal the vent on the coffee package, if there is any.
The aroma of coffee disperses very fast after the bean is grinded. That's why ideally, it's better to grind the beans before brewing it. There are manual and electrical grinder, choose the ones which you can adjust the level so that you can play with the coarseness to experiment different tastes.