Rather than re-invent the wheel, I thought I'd respond to Michael Solender's question by referencing the helper site that solved the problem for me. It's got clear diagrams and instructions.
WARNING: You might need to muck about with the HTML of your template to make this work. I did.
Blogger Widgets: Official Sharing Buttons on Blogger: "Blogger has been rolling out new features to improve the looks and usability of the blogs. Blogger is now testing out a new Social Sharin..."
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