.not-incompare .re-icon-compare:before{content:"\f643"}.fa-analytics:before {content: "\f643";}
you can place this in theme options – general options – custom css
Then, change f643 to code number from icons page RH icon
Choose any icon on site, click on it and find unicode on inner page of icon
Don’t remove “\” symbol, replace only unicode. You can also find how to change icons in header