Make the following directories writeable for your webserver:
temp/
wwwroot/media/cache/
wwwroot/media/src/ (for uploads)
Example command for Linux + ACL:
sudo setfacl -R -m "u:www-data:rwx" temp/ wwwroot/media/cache wwwroot/media/src
sudo setfacl -R -m "d:u:www-data:rwx" temp/ wwwroot/media/cache wwwroot/media/src
Apache: Point your webserver to the wwwroot directory, a .htaccess file is already available.
IIS with Ionic Rewrite: Point your webserver to the wwwroot directory, a iirf.ini file is already available.
For other webserver configurations: https://silex.sensiolabs.org/doc/2.0/web_servers.html