Wordpress - where should I place editable CSS -

Wordpress - where should I place editable CSS -

where place things header's image, background color, background image...? should add together them html code? or add together pieces of css functions.php?

also, when add together code head section functions.php - loaded automatically, or should add together more head section myself?

you can alter style.css css alter , header.php header section,footer.php footer section home content index.php file

you can phone call function function.php file in these files

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