The tutorial seems simple enough. You choose the boy trekker character, select a background, insert the keyframes, create the motion tween and then move the background to create the illusion of a boy walking. Every time I follow the steps though, my character is walking in place as if he's on a treadmill. I have tried Adobe products in the past but never spent much time with them because I wanted products that were less frustrating. However, almost every YouTuber I admire tells me that they use Adobe products when I ask them what they use and so I want to stick with it this time. Please help.
I'd suggest you approach it methodically and learn how simpler things work first.
Some tutorials are available here:
You may want to buy the excellent "How to cheat in Flash" book by Chris Georgenes.
If you don't know what you are doing, you will be prone to making many small mistakes which lead to frustration and you will feel discouraged.
Just a warning: Avoid Motion Tweens and Bones. Both are very difficult to control and have no practical application in animation workflows.
Use only Classic Tweens and Shape Tweens.