You will need to locate the addon’s installation in either your community folder or official folder depending on where you purchased it.
From there, replace the file in inibuilds-aircraft-a350\SimObjects\Airplanes\inibuilds-aircraft-a350-900\panel and inibuilds-aircraft-a350\SimObjects\Airplanes\inibuilds-aircraft-a350-1000\panel
Let me know if you have any difficulties finding these paths!