How can I create a 24-bit color file in Photoshop

Hi,

I need to upload a photograph and it needs to be 24-bit color; with Photoshop I can only create a 16-bit file. How can I make a 24-bit color file? Below is the information from the site that I try to upload the photograph. Thanks!

Image Color Depth:
24-bit color [Note: Color photographs are required. Black and white, monochrome images (2-bit color depth), 8-bit color, or 8-bit grayscale will not be accepted.]