Photoshop Element, I want to do this : see pictures [Apply photo to a cushion]

This is a 2-step process using a clipping mask.

Open the file with the pillow

Double click the background layer to convert it from a locked layer to a regular layer

Activate the Magic wand tool, click on the white background, hit delete on the keyboard

Invert the selection (CTRL+I)

Set your foreground color chip to to black

Go to Edit>Fill selection>foreground color

Go to Select>all, then Edit> Copy

Open the picture file of the girl with the doll

Duplicate the background layer, and shut off the visibility of the background layer by clicking on its eye icon

With the background layer still active, go to Edit>paste

The layer with pillow filled with black should be between the Background and background copy layers (Layer 1)

Link the Background copy later and Layer 1 (CTRL+G)

Activate the move tool to position Layer 1 to obtain the cut-out

Create Layer 2 as shown for a new background