You can still get the free bundle of assets at this URL : construct.net/en
The Beginner's guide to Construct 2 does contain the assets within the tutorial itself for you to right-click and download.
construct.net/en
The platform tutorial relies on assets which are provided when you own a license.
Go to your downloads page and click the link "Download included asset bundle" underneath the "Download" button of your license if you have one. - construct.net/en
If you do not, it is up to you to use any other type of assets to complete the tutorial (which is the basic of how things work in Construct).