How do I restart Apache ?

You may restart Apache service via Services management page in Parallels Plesk Panel:

Parallels Plesk Panel 8.x: System -> Server -> Services Management: Web Server (Apache)

Parallels Plesk Panel 9.x: Main menu -> Home -> Services Management: Web Server (Apache)

Also you may restart the service from command line:

on RedHat-like operating systems:

~# /etc/init.d/httpd stop
~# /etc/init.d/httpd start

on Debian/Ubuntu:

~# /etc/init.d/apache2 stop
~# /etc/init.d/apache2 start

on FreeBSD:

~# /usr/local/psa/rc.d/httpd stop
~# /usr/local/psa/rc.d/httpd start