As in photoshop to put the background

In the document where you need to put the background, create a new layer. Make active the window you want in the workspace of Adobe Photoshop. Press Ctrl+Shift+N or use the menu by selecting Layer, New, "Layer...". In the Color list dialog that appears, select None. Press the OK button.

Make the newly created layer at the bottom. In the main menu, choose Layer, Arrange and Send to Back or press Ctrl+Shift+[.

Open or create a background image. In the first case, press Ctrl+O or select File and "Open..." in the dialog that appears, select the desired file and click "Open". In the second case, create a new document in Adobe Photoshop by pressing Ctrl+N or selecting the menu items File and New, and then using tools and filters draw a desired picture.

Select the background or the portion of the background. If you need only part of the image, activate the Rectangle Marquee tool, select the area you want them. If the image you want, press Ctrl+A or select All in the menu Select.

Copy the selected background to the clipboard. Press Ctrl+C or select Copy on the Edit section of the main menu.

Paste the copied background layer you created in the first step. Switch to the desired document window, press Ctrl+V or select Paste in the Edit menu.

If the inserted fragment of the background differs in size from image, to which he added, adjust them. Use the free transformation activated by pressing Ctrl+T or by selecting the Free Transform in the Edit menu. You can also apply the deformation scaling, selecting Scale Transform section of the Edit menu.

Change the type of the current layer, making it a background. In the main menu, choose Layer New Background From Layer.