The place to start when you are designing your dream kitchen is with a dimensional diagram of your kitchen space. On a large piece of graph paper, draw the outline of the kitchen space, including any doors or windows that you will have work around while you design your kitchen. Accurately mark where your plumbing and electrical supplies are located. You can move plumbing and electrical supply points, but this involves more time and money, and it is always easier to accommodate existing service supplies into your design, if practical.
Once you have completed all of this, your order is constructed for you, finished to your specifications and delivered. The cabinets can be professionally installed for you or you can do this yourself. Online kitchen design is easy when carried out this way, and knowing how to do this should give you the confidence to design your kitchen online.