Let's go over the exercises you were given at the end of the last video. You should have run the following commands:
ng new thinkster-io --routing --skip-install -d-
ng new thinkster-io --skip-git --style scss --dryRun -
ng new thinkster-io --routing --prefix tio --style scss
Yours might look slightly different. For example, the flags might be in a different order; you might have used the aliases differently than I did; or maybe on the second one, you used a different stylesheet format, but your commands should look very similar to this.