The one thing I did not put into Preference was social icons, so I am guessing you are using a plugin?
As for where to put them in the header, I’m not sure where exactly you want to do that but the bad news is that you will more likely have to do some custom coding to the theme for this. You will also need to refer to any documentation for the social networking plugin (if you are using one). Normally any social plugins used in Preference will have a couple places they are put into which is either at the end of a post or in a widget position. Others will have code you copy and paste into the theme but it’s really going to be dependent on the theme because you won’t be able to put code just anywhere.