Need Icons / Customization for navigation folders

Site URL: https://www.supersizesocial.com/

I have 2 folders in my navigation bar 'instagram growth' and 'instagram powerlikes'. Both of these folders have several options that link to other pages.

I just need the folders themselves to have small icons next to them. I can add the image myself I just don't know the code to put an image in the first place. 

There is also another link 'customer hub' - this is a membership area via an external platform. I'd like to put an icon next to this as well and do something else to it to make it stand out a bit more such as making it bold. Or even better just turning the 'customer hub' link into a button (already used up my button for a different page!). 

Appreciate any help I can get!

Try adding this to Design > Custom CSS

a.header-nav-folder-title[href="/instagram-growth-services"]:before {
    content: "";
    display: inline-block;
    background-image: url(https://cdn.pixabay.com/photo/2022/04/19/08/32/relax-7142183__480.jpg);
    width: 30px;
    height: 30px;
    background-size: cover;
    background-repeat: no-repeat;
    margin-right: 10px;
}