Absolutely correct. I am slightly worried that “You need a 12 volt commercial power pack or power supply( $$$) connected to the 110 AC wall outlet” could be misunderstood by a newcomer. There are controllers that need to be fed with 12V DC and these MUST NOT be connected to mains electricity. EVER! What you need is either a control unit incorporating a transformer (and rectifier, unless your mains supply is Direct Current) and a control knob with which you can regulate the voltage (to control the speed of the locomotive), or you should have a separate transformer (+rectifier) supplying approx. 12V DC to your separate 12V DC controller that has a voltage regulator knob but does not incorporate its own transformer. In the latter case, great care needs to be exercised if the transformer does not come in its own earthed and/or double-insulated case.

As this blog goes worldwide we must not assume that the country that the OP is in uses 110 volt mains (could be 220 or 230 or 240 or 100 volts AC). I do not know a lot about DCC but I understand that the track voltage may be up to 18 volt AC not necessarily 12 volt DC

Starting at the beginning.
1st You must have wiring for 110 AC volt electricity.

2nd You need a 12 volt commercial power pack or power supply( $$$) connected to the 110 AC wall outlet.

3rd You would need a train set with track and a locomotive that will operate on that track.

4th you need two wires from the power supply to the track.
Connect the wires to the DC or direct current {that what DC is} terminals on the power supply.
Some connector tracks have screw terminal as part of it.
Other tracks do not have this.== which is OK because you solder the wires (one to each rail)

5th the big test. (drum roll)
a. place the locomotive on the track
b. turn on the power supply to the AC wall outlet and adjust the power ( speed ) of the locomotive as the locomotive starts to move.

You can also find free online courses on basic electronics, which will be worth your time to follow.

Having a good basic working knowledge of electrical circuits is important in model railroading.

You can use both power packs on one railway using analogue control, as long as they are connected to parts of your railway that are isolated from each other electrically. Get one of the simple, inexpensive “PECO Shows you how” leaflets from http://www.pecopublications.co.uk or your local model shop. There are three on this subject, and if you’re ordering from outside the UK, you might as well get all three – I expect the postage will be more than the cost of the leaflets. There are other publications available, which may cost more but go into more depth. I have no connection with PECO other than as a satisfied customer.

Wrap clockwise, so that it doesn’t tend to loosen as you turn the screws.