There are many helpful people here on RadioReference, so don't give up on the website just yet. People can't give you a step-by-step answer on how to program a scanner until you have a particular model in hand. It would be like someone asking "Tell me how to prepare a meal." The answer would depend 100% on what that meal was. Instructions would be totally different for baking a cake than making a peanut butter and jelly sandwich.
Most current day scanners will be programmed in a similar manner, but not exact. So, there is no set of steps 1 through 10 that can be given to answer your question. The most general answer I can think to give is that using a computer to achieve the programming makes things a LOT easier than trying to push buttons on the scanner like old times.
YouTube might hold some good information for you regarding the programming process for different scanner makes/models. Watch people work with the model(s) you're interested in, and use that to help make a decision on which scanner you're going to purchase.
Once the make/model is determined, THEN we can start giving you more detailed information, and you'll feel like your questions are being answered