Installation of a rain barrel is not a particularly complicated affair.  The actual steps involved and hardware required will vary to a small extent depending on your location and the rain barrel you choose. 

If you want to buy one, check out the large selection of rain barrels at Clean Air Gardening.

There are several different types of rain barrels made from recycled food barrels, varying in size, shape and color. Some of them come in a terra cotta (read orange) color, and some of them come in blue, white, gray, black, etc. The most common sizes are the 50 gallon rain barrel and the 60 gallon rain barrel.

The rain barrel installed here is a 60 gallon rain barrel that came from Clean Air Gardening.

Use gravity to your advantage here. 

First open one end of the box, fold over the flaps and turn the box open side down on the ground. 

Then simply lift the box off of the rain barrel.

That was simple, wasn't it?

Once the barrel is out of the box, there is actually very little assembly to do to the barrel itself.  

The spigot will need to be inserted into one of the two available locations.  The upper location is a good choice if the barrel will be sitting on the ground.  

In this installation we will be setting the rain barrel on concrete blocks, so that we can use the lower spigot location and drain the barrel fully as needed.  The instruction sheet advises that you don't use tools to tighten the spigot or the plugs in the fittings in the sides of the drums. This is a little bit misleading, as you will need to use a wrench on the fitting itself to keep it from turning as you screw the spigot in by hand.  

Please note that you want to be very careful putting in the spigot, because the spigot is very easy to cross thread.  If it does not appear to be going in straight, do not force it. Back it out and start over.

Pay attention to the label. In addition to traveling through the polluted atmosphere and picking up who knows what in the process, the water that you collect in the barrel also has gone across your roof in through those not exactly sanitary gutters.  Great for plants or washing your car, but not so good for people without some treatment.

The  rain barrel will need to be located near a down spout from your rain gutter, if you want to get water from a downspout.

If you don't have downspouts, you can often still use a rain barrel. You just have to find one of those troughs where two parts of the roof come together and water pours out whenever it rains. Place the rain barrel under one of those spots, and you'll get plenty of water.

Generally, downspouts are attached to the house by straps and will need to be dissasembled.  Remove the screws holding the straps to the downspout and any screws that may have been put in to attach the spout to the gutter.  Once the brackets have been released the downspout can be removed and set aside.

When removing the screws and detatching the downspout, remember to wear safety glasses if you are using power equipment. We wouldn't want you to hurt yourself, would we?  

Now that the downspout is out of the way, we need to find a way to redirect water flow into the top of the rain barrel.  

There are several comercial products available for this purpose.

The Garden Water Saver downspout redirector is an excellent choice in that it attaches inline between joints of your spout and once your rain barrel is full water is automatically directed back out through the original spout.  It does require a small amount of cutting with tin snips in order to fit properly. Unfortunately, our downspout in this example is too large to use the Garden Watersaver.  

It is important that the concentrated water flow be directed away from the house or into the barrel as too much water in one place near the house could result in foundation damage.  Therefore it is unwise to simply let the water fall from gutter into the barrel for any significant distance.  For this particular installation the best solution was to use a plastic flex house available at most home improvement stores.  The flex hose can be secured using the existing straps and expanded and directed to the needed position. You can also find these flexible downspout redirectors online.

Your installed rain barrel should be placed on a reasonably stable and secure surface, like the wide concrete blocks in the picture above.  A barrel this size will weigh a substantial amount when full of water. Water weighs something like 8 pounds per gallon, so you can see how it adds up quickly!  

If you elect to use the lower mounting position for the spigot, be sure there is sufficient clearence for you to attach a hose in order to use the water you collect in the barrel.  The installation process is not particularly complicated as you just saw, but it does require some planning.