I'm already lost, don't know how to use an external power supply

I live in North Wales so I'm the wrong side of "The Pond" for best advice as our mains supply is different (and more dangerous), but this is a start.

From the image on the link, it looks as if the two right hand terminals are the low voltage output, but I can't make out the symbols on the other three. Perhaps the left two are AC inputs which usually have a "~" symbol or similar, sometimes with the voltage range. That middle terminal might be an earth (ground) for the mains input, or 0V for the output side. It looks as if you slacken the screw, insert bare end of wire then tighten screw  to clamp wire. I can't see what the extreme right end (blue bit) is.

Personally, I'd put it in a case with leads from its terminals, especially the mains input ones, to insulated

terminals on the outside. At least put some insulating tape over the mains input terminals after you've connected the mains lead. I'd also include a fuse in the mains live lead (rated at 20 divided by your mains voltage)  and perhaps a resettable fuse in the output with a rating to protect your equipment. That might be much less than the power supply's 6A rating; perhaps only 1A.

I hope this forms a basis for your thoughts or for questions to ask people locally. Best wishes & stay safe.

Old Frank

Best not use that type of power supply it's generally used inside enclosed equipment.  Also it has a 6 amp output so if you make a mistake in your soldering or create a short circuit in a bread board it will get instantly fried.
Best option is a variable bench power supply as in the following example;

http://cpc.farnell.com/_/in05524/power-supply-bench-led-30v-3a/dp/IN05524

Try RadioShack or any local hobbiest store for a Variable Bench Power Supply

You can use it for lots of projects requiring different supply voltages, charge small batteries and most importantly limit the current so that any errors will kill the supply voltage and not the project.

Hope this helps.

Mark's right about this type being used inside equipment. If it was sold as an external power supply you should return it and tell them that it isn't. That's why my first move would be to case it. Snag about the price of the supply Mark recommended, but it is a very good one, would last for years and save you much grief.

Thank you both for your answers. I will look into getting a bench power supply as it sounds much safer and may prevent me from destroying my projects as I continue to learn.

Thanks again!