You can position the social icons absolute wherever you need them and they will then float...
div.g-social {
position: absolute;
top: 10px;
left: 10px;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.