Answered: Button in header part of the page

For your own link : go to https://your-site/admin/pages & on bottom => Add link

If you would use Font-Awesome :
Open your qa-style.css (in theme folder on your ftp)
Search : .qa-nav-main-custom-1 .qa-nav-main-link:before
Replace:  

.qa-nav-main-custom-1 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Free"; font-weight: 900; content: "f0ca";
}

.qa-nav-main-custom-2 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Free"; font-weight: 900; content: "f128";
}

.qa-nav-main-custom-3 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Free"; font-weight: 900; content: "f07c";
}

.qa-nav-main-custom-4 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Free"; font-weight: 900; content: "f042";
}

/* DISCORD*/
.qa-nav-main-custom-5 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Brands"; font-weight: 900; content: "f392";
}

/* DONS */ 
.qa-nav-main-custom-6 .qa-nav-main-link:before {
font-family: "Font Awesome 5 Free"; font-weight: 900; content: "f4c0";
}