how can you make such a header (sticky)?

[Alex5E34]

hello everyone!
how do you make a header like this (sticky)?
see the top of the site

[Risky links removed by moderator as a potential threat.]

[Nancy OShea]

Use CSS. See links below.

• https://www.w3schools.com/howto/howto_css_fixed_menu.asp
• https://www.w3schools.com/howto/howto_js_sticky_header.asp