Please read and follow the steps below and try to understand carefully:
1. Open
a. index_body.html
b. search_results.html
c. viewforum_body.html
in you favorite code editor
2. Search & Find the icon code <i class="fa fa-bar-chart"></i>
in
a. index_body.html
b. search_results.html
c. viewforum_body.html
3. Replace your chosen FontAwesome icon code instead of this icon code <i class="fa fa-bar-chart"></i>
4. Remove the phpBB cache and check the change
Best Regards,
ThemeLooks Support Team