To Check Out a File

You can edit a file associated with a document. When you check out a file, the document is locked. A file can be checked out providing that you have the appropriate permission, and the document approval status is Not Approved.

Checking out a file prevents others from accessing the file until it is checked back in again.

You can also revert a checked-out file to checked-in status, via the Cancel Check Out option.

Open the document for which you want to check out a file.
On the Files tab, select the file that you want to check out.
From the Actions menu, select Check Out.
From the Save list, select one of the following:

Save: To accept the filename and save the file into the default file downloads location

or
Save as: To browse to a specific location and/or change the file name.

The file is checked out.