Adding code to header for ShareThis button bar

I'm trying to add ShareThis(.com) bar to office 365 website. Code has to be added
to the header, but when I add it to the little  "t f SIGN IN" block in the upper
right of the heading, the code is visible on the website page and the clickable bar does not appear. I'm not very
technical - I must be doing something wrong - any suggestions? I tried adding
the individual buttons (Pinterest, Google + etc.) but they take up so much background
space, that my content gets pushed down the visible page with each button
added.