Help with editing

[Blazing Angel]

Hi,

can anybody tell me how I can add another picture in the background as a watermark? I have a wedding photo with the bride and groom looking around a tree at each other. The tree has a wide split in the middle and I'd like to put a faint picture of their daughter who was the bridesmaid in between it. I have Paint Shop Pro 7, Photobase 5 and a trial of Adobe Photoshop Elements 6.

Thanks