Google Drive / Getting Started with Drive 

Rename documents in Drive

Each file stored in Google Drive should have a unique name to identify it. All files, including Google Docs, Sheet and Slides, can be named after they have been created - if you need to rename an existing document, this can be done via the docs list. 

To rename a document in the docs library:

Type a new name for the document, then click on OK

You can also rename a document by right-clicking over the document and choosing the Rename option: