tasty theme's css to edit mobile font is missing

Hi!

Tasty theme's CSS to edit mobile font is missing. I am quite clueless about the exact spot where I ought to insert the following CSS code.

@media (max-width: 768px) {
body {
font-size: 16px;
}
}

Also, I want to have the posts displayed in columns for each category page but not on my homepage. The problem is that the CSS to edit the number of columns in each category page is also missing. Or do I just need to insert the ff. CSS codes somewhere? If there is a specific spot where I should add these codes..where exactly shall I place them? Thanks in advance.

add_filter( 'generate_blog_get_column_count','tu_search_column_count' );
function tu_search_column_count( $count ) {
if ( is_search() ) {
return 33;
}

return $count;
}