What must you do to re-record a rewritable DVD plus RW?

First, you must insert the DVD+RW disc into a DVD burner that supports ReWritable media. In Windows, the DVD will usually open as a directory on your computer. Select any files you don't want to keep on the DVD after you finish re-recording, then delete them. Copy any files that you do want on the DVD after you re-record, and click "Burn to disc".

There are multiple applications available for Windows, OS-X, and other operating systems, and while the specific steps for re-recording on a DVD+RW are, for the most part, different, the basics are all the same as described above.