In Google after you log in find your picture, or the default picture in the top right corner. When you click on it a window will pull down and you should click on the word Privacy. This will open a webpage that will give you lots of information about how to be more secure. If you want to set up 2-step authentication slide down the page and click to "find out more about 2-step authentication.
Follow similar steps to set this up in Yahoo, Twitter and other programs. The choice will be found in your settings under security or privacy.
The more secure your computer is the more difficult it is for anyone, including you, to use it. I like the advice of Socrates "Know Thyself". How old are you? How good is your memory? What do you use your computer for? How often do you use computers other than your own? Do you have a cell phone and do you use Text Messaging?
For someone who uses a computer all of the time for business purposes or for regular banking it is a good idea to be as secure as possible even if it is frustrating sometimes. For someone who mostly plays solitaire and sometimes gets online to do email it may not be worth the effort. Then there are all of the many cases that fall inbetween. So, know yourself, is the best advice that I have.
Since we are talking about security I thought I would also mention the Captcha Codes. Wikipedia says it stands for Completely Automated Public Turing test to tell Computers and Humans Apart.
You often have to fill them out at the bottom of a form or application that you are submitting. They are getting more and more difficult to interpret. They were devised to make sure that it was a real person who is filling out the form. Today there are robot computers that can fill in forms and send notes, but they cannot read pictures of letters and numbers.
If you cannot read the code on the page that you are on there is a speaker you can click on to hear the audio of the captcha. You can also press the circle arrows (or reload) to get a new code. There are several really tricky letters and numbers to read (L, l, I, and 1 for example), so never feel like you are stupid. You are SO much smarter than any computer.