Add some class???

Hi, I am trying to customize the event-blocks template but I don’t know how to do… I know well WordPress and I’ve found the .php file I have to modify but I would like to change some things…

In every single event page (in backend), I would like a text area where I can put some text.

Usually in wordpress I use things like this:
«
array(
‘name’ => ‘Next matches (Date and time of the game)’,
‘desc’ => ‘Insert please date and time of the game(ex.: 26 may 21:45).’,
‘std’ => ”,
‘id’ => $prefix . ‘ab_nextdate4’,
‘type’ => ‘text’,
»

How can I do in sportspress?

Thanks you very much,
Ben

https://wordpress.org/plugins/sportspress/