To convert an Angular project to use the Angular CLI, you could follow these steps.

1. Install the CLI

npm install -g @angular/cli

2. Create a new CLI Project

ng new my-first-project
cd my-first-project
ng serve

3. Copy your existing code files into the new CLI Project

4. Configure your Angular Workspace

Differences between Angular CLI and Other Build Systems

Notes from Migrating a project to Angular CLI build system

• Angular CLI may use multiple tsconfig.json files (be sure to setup dependencies between files correctly)
• ng serve and ng test compile your typescript into memory rather than physical files.
• If ng test doesn't work and gives cryptic errors look into the pollyfills.ts file and start uncommenting lines.
• Consider locking package.json versions with exact version numbers, shrinkwrap, lockfile, or yarn. There is no joy in debugging @types, tsc versions and incompatible modules.
• Building with ng build --prod (which uses AOT compilation) is a lot more strict than the default typescript rules with ng serve.
• Using sass for css:
  1. When creating new project: ng new my-first-app --style=scss
  2. Or modify angular.json:

"schematics": {
      "@schematics/angular:component": {
      "styleext": "scss"
    }
}