photoshop cs4 WORKSPACE

To create a new document, click File > New. This will open the Document Setup.

 

Document setup dialog box

 At here you can name your file, set up the correct page size, and orientation for your document. 

Page Size and Orientation
Change the page size by typing in new values for width and height. Page size represents the final size you want after bleeds or trimming other marks outside the page. In the Preset dropdown menu you can find such common sizes as letter, legal, tabloid, etc. Typing in exact values for Height and Width gives you more control over the size and orientation of your page.

Resolution
Resolution is a number of pixels on a printed area of an image. The higher the resolution, the more pixels there are on the page, the better is the quality of the image. However, high resolution increases the size of the file. The standard recommended resolution for printed images is 150-300, for Web images it is 72.

Color Mode
Choose a color mode that will best fit your project. For example, when making a graphic for a web site, choose RGB. When making an image for print, choose CMYK.
Background Contents
Choose the background: white, color, or transparent. When you have entered all of your document settings, click OK.

This is the workspace after you set up on the Document Setup.

HoW tO oPeN tHe ImAgE in photoshop CS4....   

 select File > Open, and then navigate to the disk drive where your image is saved.

Choose the image file and click Open. At this point, you may want to save your image under a different name so that you can always have the original to fall back on in case of a mistake. 

Here is the workspace after adding the image

To save your file, select File > Save As and type in the new name of the file in the dialogue box. Now you can start to edit your image by using the tools or effect in photoshop.

Enjoy your work time !!! =)