Sticky Menu - Gap at the top

I'm so sorry, I'm having the same problem again on another new site. I've been given these fixes before:

.affix.bd-affix-3 {
top:0!important;
}

and

.affix.bd-affix-2 {
top:0!important;
}

neither of which are working on my new site.

Please can you give me a fix and tell me how to inspect the page to find out how to fix it for future websites?

https://rgc.ywdw.co.uk/index.php/blog/rgc-win-the-top-tweeter-award

Thank you, kind regards