How to customize vhost.conf on plesk 12.50

Hello, i should edit my vhost.conf for one domain on my vps. I use plesk 12.50 on centos 7.

I should add directive:

ServerAlias "*.foo.bar"

to permit wordpress to manage multisite.

I have followed many guides, but i'm not be able to edit configuration.

I have tried to edit /var/www/vhosts/foo.bar/conf/vhost.conf , but file not exist. I have created this one and i have added directive. After that i have launched:

/usr/local/psa/admin/sbin/httpdmng --reconfigure-all
service httpd...

How to customize vhost.conf on plesk 12.50