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You misunderstand. Your blog is already equipped with these. All you need to do is activate the feature so you can use it.
To use the graphic smilies supported at WordPress.com, go to Dashboard -> Settings -> Writing and check the box next to
____ Convert emoticons like :-) and :-P to graphics on display.
Then click “Save Changes”
When you use the keyboard shortcuts in posts the yellow smilies will appear when you publish them.