First we have to make all of those buttons.
>>Read the following post for making a Google+ button. Once you get the code of your desired button, save it in note pad.
>>Then make a new Facebook like button. on the Facebook develpoers page.
>>Now go a head and make a new Twitter Follow button.
Once your buttons are ready follow the next step.
Now align your buttons as shown in the code below.
<div style='float:left'>If you don't have a Add a Gaget section above the menu bars, go a head and read: Add Another Widget Section (Gadget Holder) To Blogger Layout
Twitter Button Code Here
Facebook Button Code Here
Google+ Button Code Here
Now place all those codes after aligning and save the widget. Hope that helped. That was pretty easy i guess.