In a Content Area open the Assessment menu and select Assignment.
Under Submission Details you find options regarding the type of submission, the number of attempts allowed and Plagiarism Tools.
Select the option Check for plagiarism with Safe Assign.
The mention concerning English language submissions means that only submissions in Latin script can be processed by Safe Assign.
If desired check also one or all of the other options.
Under Grading Options and Display of grades you will find other options for which you normally use the default settings.