Hi René,
"anyway I couldn't add font awesome with Generico code, I don't know why, only show me the Generico Code with the { }"
This problem is due to not setting the Generico filter to work for both Content and Headings.
To fix it and make the Generico method work, go to Site administration > Plugins > Filters > Manage filters. Once there, look in the, Apply to, column for Generico and set the drop down to, Content and headings.
Using Generico is preferred to changing the code like you did because your changes will get wiped out when you upgrade Moodle. Using the Generico filter, your icons will still be there after each and every Moodle upgrade.