1. Go to `Settings/Languages & Frameworks/PHP`.

2. Set `PHP language level` to `7`.

3. Click button `...` of `Interpreter` input.

4. Click the `+` icon to add new interpreter.

5. Enter the following:<br>
&emsp;`SSH Credentials`<br>
&emsp;`Host: 127.0.0.1` `Port: 2222`<br>
&emsp;`Username: vagrant`<br>
&emsp;`Auth type: Password`<br>
&emsp;`Password: vagrant`<br>
&emsp;`PHP executable: /usr/bin/php`<br>

6. Save changes.

7. Go to `Settings/Languages & Frameworks/PHP/Servers`.

8. Click the `+` icon to add new server.

9. Enter the following:<br>
&emsp;`Name: homestead.app`<br>
&emsp;`Host: homestead.app` `Port: 80`<br>
&emsp;`Debugger: Xdebug`<br>

10. Check `Use path mappings`.

11. Add mappings:<br>
&emsp;`C:/path/to/project` > `/home/vagrant/project`<br>
&emsp;`C:/path/to/project/public` > `/home/vagrant/project/public`

12. Save changes.

13. Click `Start Listening for PHP Debug Connections` in PHPStorm interface (at the top-right corner).

14. Install `xdebug helper` Chrome extension and set `IDE key: PHPSTORM` in configuration.

15. Go to `homestead.app` and enable `xdebug helper` Chrome extension.

16. If you are using a REST Client, simply add `?XDEBUG_SESSION_START=PHPSTORM` at the end of the URL and `Cookie:XDEBUG_SESSION=PHPSTORM` to the request headers.

17. Now you can set breakpoints and start debugging!