1. Find the button you want to add. Copy the HTML code in the box beneath the button.
2. Click on your blog's layout tab.
3. Click on 'add a gadget' in your sidebar.
5. Paste the button's code into the big box. Add a title if you wish.
6. Hit save.
8. You can click and drag it to where ever you want to put it in your layout.
9. Preview your blog and then hit save!
Straighten Up The Buttons In Your Sidebar
How To Rearrange The Buttons/Gadgets In Your Sidebar
How To Center A Button