What is a one-sentence summary of the following article?
Look for an Alt code from reliable sites.  Alt code sites have lists of symbols with their corresponding Alt codes. Just scroll through the list until you find a symbol you want to use. Once you’ve decided on a symbol you want to input, take note of the number associated with the symbol. This is what you will be typing. Turn on the Num Lock on your keyboard by pressing on the key, which is usually located close to your number pad on the upper-right portion of your keyboard. Click on a blank area of any text field, hold down the Alt key (for Windows) or the Option key (for Mac), and using the number pad, type in the code numbers associated with your symbol. Let go of the Alt / Option key, and the symbol should appear on the text field. If this does not work, try using the other Alt key on your keyboard, and it should input the symbol.

Summary:
Find an Alt code. Remember the code number. Enable Num Lock. Type in the code.