The Image in this widget can be Changed to Font Awesome by changing the following code
<img src='https://2.bp.blogspot.com/-HWl2PCk1T_g/XqqDylYxjCI/AAAAAAAAONY/h6Yr9fkzWhQ35ob37L9PnxiX7ExTmns1gCLcBGAsYHQ/s50/basic.png' alt='Basic'/>
Please go to Blogger>> Template>> Edit HTML
Place the code below right above the code ]]></b:skin>
Save, or click the Save Icon.
Furthermore, to install the widget, the code below is simply placed where you want, like in the blogger layout, edited HTML or can be placed in certain posts (HTML mode as shown).