I'm getting the error below..
!!Error in Package Installation
At least one error was encountered during a test installation of this package. It is strongly recommended that you do not continue with installation unless you know what you are doing, and have made a backup very recently. This error may be caused by a conflict between the package you're trying to install and another package you have already installed, an error in the package, a package which requires another package that you don't have installed yet, or a package designed for another version of SMF.
Installations actions for "Google Search Box With Results":
Installing this package will perform the following actions: Type Action Description
1. Execute Modification ./Themes/default/languages/Modifications.english.php Test successful
2. Execute Modification ./Sources/ManageSettings.php File not found
3. Execute Modification ./Themes/default/index.template.php Test successful