Creating a New Image
To create an image from scratch:
1. From the File menu, select New.
The New dialog opens:
2. Enter a name for the image.
3. Enter the width, height, and resolution of the image you want to create, or select a preset from the Preset menu at the top of the dialog. The Presets menu is a handy way to select image sizes that are common for print and Web use.
4. Select a color mode. The color mode determines the number of colors that displayed in an image as well as the number of channels and the file size.
5. Select the background contents—either white, color, or transparent.
6. Click the Advanced 
button to expand the dialog and choose a color profile. Unless the image will be used for video, choose Square for Pixel Aspect Ratio.
Note that as you make your selections, Photoshop displays the file size in the lower right portion of the dialog.
7. To save your settings as a preset, click the Save Preset button, or click OK to open the image without saving your settings.
