What is a max file download size for website

Hello

This has possibly already been solved however I can't seem to find a post I understand properly as I am very much a novice with plesk. Basically my problem is when downloading Wordpress I go to install a theme it said that the max file size wasn't high enough so I did a bit of googling and it said I needed to add a php.ini file so this is what I did to no luck however the message that was displayed from now on says:

The uploaded file exceeds the upload_max_filesize directive in php.ini.

I've tried to follow the documentation listed: Changing the Maximum Upload File Size

However unfortunately i have no idea how to restart the web server by running the /etc/init.d/psa restart command to test to see if this will fix the issue, however with this being a command that affects the whole server I'm reluctant to do so as I don't want to effect any of the other websites on the server.

Any help would be awesome

Michael