The pack used for the "how to make a platform game" tutorial is part of the assets pack you get when buying a license for construct2.
Use your own sprites/textures to keep up with the tutorial.
This very part of the tutorial allows you to import a sprite-sheet (different frames all saved in a single image file, and automatically "cut" by C2 when importing the image).
If you don't have the same assets, just use assets you can find on the internet or in the Tools/resources forum.