First, hire a qualified electrician to install an electricity supply and an outdoor outlet to an easily concealed location close to the fountain. Then dig a hole larger than the reservoir.
Remove any sharp stones from the hole and pack damp sand around the edges, sides and base. Place the reservoir in the hole, and use a spirit level to check that it is level in all directions.
Pack more sand around the reservoir, as necessary, and check that it is level again. It is essential that your fountain is horizontal to prevent water from draining out, and to ensure that the pot on top will be stable.
When level, place the pump in the reservoir. You may need to fit an extension pipe onto the pump to reach through the hole in the base of the decorative pot. Put the lid on the reservoir, and over the pipe from the pump.
Attach a long section of pipe to the water flow adjuster. Then attach this to the pump pipe in the base of the pot. Trim the water delivery pipe so it reaches just below the rim of the decorative pot.
Use a watering can or hose to fill the reservoir through the holes in the lid, and fill up the decorative pot to just below the delivery pipe.
The electrical cord must be protected by special tubing, which an electrician can advise you about. Make sure that all electrical connections in the garden are fitted with a ground fault circuit interrupter (GFCI).
Plug in the pump and check that it pushes the water over the top of the pot, and adjust the flow as necessary. Disguise the reservoir with pebbles and gravel, leaving a gap to allow you to fill it up; you need to do this once a week in summer.
Plant up around your pool, leaving a margin between your planting and the reservoir, to avoid dislodging it. Plants from the Mediterranean, such as euphorbias, lavender and rock roses make great companions for an urn. If you prefer a more traditional look, try roses, honeysuckle and daisies.