How to Copy & Paste in Photoshop
Like most computer programs, Adobe Photoshop allows you to copy and paste selections to create duplicates or move data from one file to another. Unlike simpler image editing programs, however, copying and pasting in Photoshop requires an awareness of image layers, positioning, color settings and size. The program also provides several advanced types of copying and pasting to help edit your image just the way you want it.
Click either the Marquee tool or the Lasso tool icon. Marquee allows you to select a predefined shape, while with the lasso you can draw your own selection. To pick an alternate version of the tool -- such as an elliptical marquee instead of a rectangular marquee -- right-click on the tool's icon.
Click and drag on an image to select the area you want to copy. If you need to add additional parts to your selection, click the "Add to Selection" icon, which looks like two overlapping squares, and select another part of the image.
Press "Control-C" to copy the selected part of the current layer. Alternatively, press "Shift-Control-C" to copy a merged version of all layers.
Open the image you want to paste into.
Press "Control-V" to paste the selection. It will appear on a new layer in the center of the image, after which you can position it using the Move Tool.