Transparency in Photoshop CS?

[rich_g85]

Hi All,
I have an image of an object on a plain white background, which I need to paste into another document, which has a gradient-filled background. I don't want to see the white background behind the object, just the gradient fill.

How do I tell photoshop to display 'white' as 'transparent' in the new document?

 

[Messiah Khan]

One way of doing it would be to select some of the white, then go to select>similar, then edit>clear. This will delete all the white, leaving it transparent.

 

[philio16]

Magic eraser -> click on the white