Before you learn to type online, you should know how to sit properly when you type, and you should know how to position your arms, hands and fingers. Some of the online typing courses will teach you how to do this. (See Resource below, Peter's Online Typing Course.)
When you learn typing online, you start off by learning where to place your fingers on the keyboard. Some online courses display a printed keyboard on their websites as a teaching tool, and the printed keyboard may have colored keys to assist you in the learning process. Instructions on how to use the home row may be given, and various keys will be identified. An online course will also teach you which fingers to use when you strike certain keys.
To help teach you how to type online, some online typing courses give you typing exercises to do. Your fingers need to know, automatically, where to find certain keys. There should be no hesitation when you type because uncertainty will significantly reduce your typing speed. These exercises will help you increase your typing speed. Tips and instructions on how to do these exercises are usually given.
Practice makes perfect, and especially so when you're learning how to type. Many online typing courses help you gain typing speed by giving you timed typing tests. Each time you type the text given, your speed is calculated and will show up on the screen in front of you. This allows you to keep track of your typing speed. You can type the text as many times as you choose. With time, you will find yourself typing faster and more accurately. Some sites even have typing tests that make learning and practicing more fun.
Some online typing courses will give you a typing certificate when you complete a course. This certificate averages your typing speed, and it can be used to prove to anyone online you know how to type. A typing certificate can also give a sense of accomplish to some typists.