Hello.
Thanks for posting your question regarding making the page header “sticky” using the Grid One Theme. Unfortunately, this is not an option that you can customize using BoldGrid. However, if you are familiar with CSS/HTML design, you can use the Customizer’s CSS/HTML editor to modify various aspects of the theme you are using. You can also try to use Google Chrome Developer Tools to identify and manipulate the website to determine what CSS/HTML is needed to attain the look you are trying to design.
I hope this helps!
Sincerely,
Carlos D.