Add a button to the header

Hi Team Kriesi,
I would like to add a ‘Donate’ button to the header which goes to a page on the site, just like the one on the in the header of Cancer Research website https://www.cancerresearchuk.org/support-us/donate
I would also like this button to be hidden from the header on small screen tablets and mobile devices, again just like on the Cancer Research website.
I’ve tried the instructions from this post but I can’t style it so it’s positioned in the middle on the right or get the colors to be pink (#bd2e89) : https://kriesi.at/support/topic/adding-custom-button-on-top-right-hand-of-enfold-header/
Any help you could provide would be greatly appreciated.
Many thanks in advance!