Fatal error: Class 'Mage_Legenda_Helper_Config'

how to remove the legenda theme from magento?
Magento has an installation of SW Legenda already in the system.

Just Installed the Porto Theme and the legenda installation is causing issues.
How can I remove the SW legenda installation so that my Porto installation will work?

Fatal error: Class ‘Mage_Legenda_Helper_Config’ not found in /home/onesma6/public_html/staging/app/Mage.php on line 547