Go to plugins > add new
Search for Sticky Menu (or Anything!) on Scroll and install/activate the plugin.
Then go to Settings > Sticky Menu (or Anything!) on Scroll
In the Sticky Element field fill in the class name you gave your section. In my case #stickybar
Important: You have to add # in front of your name here
In the Space between top of page and sticky element: (optional) field I fill in 95. I use a fixed navigation and I want the stickybar underneath it. So I have to add the height here of my navigation. In my case this is 95px but if you use different navigation size it can be another number. You can trial and error the size until you are happy or use a tool like Google inspector. In case you navigation is not sticky then you can leave this field blank.
In the Do not stick element when screen smaller than: (optional) field I fill in 981 which means that this section will only stick for desktops.