If you have downloaded the installation file from the Internet your next step is to install the program by double clicking on the installation program (shown below).

If you have the choice, you may install without downloading the file. In this case you would be installing directly from the Internet. When you see this dialog box, click on the Run button rather than the Save button.

In either case, when you install the program, the first screen you will see when the installation begins is below:

Follow the directions step by step by clicking on the Next button on each screen. That will install Nvu on your computer and you may use it as soon as the installation completes.