@ import css to change header and colours in sheet

Hey , been trying to change mny header image and theme colour for ages – I know simple css and that I need to edit my css file – however it says

Import Stylesheets
———————————————————–*/
@import url(“stylesheets/master.css”);

where the css file is normally – how do you @ import the style sheet so I can edit it ?pls

I cant find any normal answers online . —

thanks if you can help that would be v awesome