The best way to learn how to shop online is to practice. Find a shopping site and click around.
Don't worry about accidentally buying things you don't want -- online stores put you through a series of steps when you make your purchase. If you don't click the "Click here to complete this order" button, your order won't go through.
Most shopping sites give you the choice to search or browse the products. For example, look at
Amazon.com.
Search
Along the left side of your screen, you'll see an orange and blue (or yellow and gray) box that says Search. The orange section contains a blank box where you can type in your keywords. That area also contains a menu that lets you limit your search to books, music, or other sections of the store. That's optional, but it can speed things up.
To find "The Rest of the Earth" by William Haywood Henderson, I can type "rest of the earth" into the little text box, select Books from the menu above that box, and click the Go button. The site presents me with a choice: hardback or paperback? I click on the paperback title.
That brings me to
the page where I can learn more about the product. If I decide to buy it, I can click the big orange button to the right of my screen that shouts "Add to shopping cart."
As the button says, I can always remove the item later if I change my mind. (In fact, I don't even have to do that -- I can wander away to eat dinner, or surf to another site, or check my email, and if I don't return to my shopping site within a certain amount of time, my order simply goes away.)
Browse
If I'm not looking for an exact title, I can choose to browse instead of search the site. Just under the Search box you'll see the Browse list.
I want a book, so I click on Books. On the books page I see some highlights in the center. I make a mental note to pick up
HP4 sometime when I'm not on deadline for an article, and I continue browsing. I click Mystery & Thrillers from the list of subjects in the Browse box (still at the left side of my screen), and so on. I can click through Amazon.com's products pretty much the same way I click through websites at
LookSmart or
Yahoo.
Most shopping sites have a similar setup. As long as you take some time to look around when you first arrive, you'll soon figure out how to get to the products you want.