I'm not entirely sure I understand your question but I assume you mean your file is flagged as "read only". Assuming, also, that this is a file you have recorded yourself, you need to right-click on the file, choose Properties from the drop-down list that appears and then check the setting highlighted in this screenshot.
Alternatively, if the file are on a read-only media - such as a CD/DVD/Blu-Ray, it will need to be copied to a writeable media - such as a HDD/SDD, to be editable.