Find a large, clean, well-lit work surface which has two or more mains power outlets nearby (RCD protected, if possible.) You will need space for your monitor, keyboard and mouse and to lay your case on its side, such that you can fit the components etc.

Collect together the necessary tools nearby, such that they are close to hand. It is advisable at this stage to set up your anti-static precautions.

Make a collection of all your new components (still in their packaging) and place them nearby, ready for use.

Unwrap and carefully place your monitor (on its stand) on the work surface, such that you can clearly view the screen. Be careful when lifting monitors as they can be extremely heavy. Ask someone for help if necessary.

Retrieve the power and signal (if supplied loosely) cables from the packaging and fit them to the monitor as instructed by its manual. Do the same with the keyboard, mouse and speakers (if you have them) such that they are ready to be used later on.

Do not connect any devices to the mains power outlet yet.