Adding an email subscription field to top menu

Hello! This is the website I’m referring to: https://entropywave.com/

I’m looking to add a simple email subscription field on the righthand side of the main menu. Similar to the one that is at the bottom of the homepage. For example, like on this website where it says “Sign up for updates” in the top menu: https://livetranscoding.com/

Anyone have any suggestions? Thanks!