how do I have a drop shadow on the header

I recommend asking in your theme’s dedicated support sub-forum for better results so its developers and users can help you with this:
https://www.ads-software.com/support/theme/sydney

More or less, this:

If your theme has a custom CSS option, use it. If not, install the plugin “simple custom css”.

#masthead.site-header {
    box-shadow: 1px 1px 12px #000;}

thanks man that worked

yeah, it the shadow improves the look — the theme is otherwise very “flat”.

Ihe theme I have, I dont no I think visually it looks great.I’m really proud of the art ive made for it also.