Photoshop merging on MAC

[law1966]

I am a beginner to photoshop!    I've added two photos to the workspace.    I click on the one I want to add, drag to the file name of second photo and once it appears I release the first.    Based on what I've seen on videos, the photo I want to add should show up as a layer on the workspace of the second photo but it doesn't.     Hope someone tell me what I'm doing wrong.    Thank you.

[c.pfaffenbichler]

» and once it appears I release the first«

Try dragging onto the canvas before releasing. 

Or simply abandon tabbed display and use floating windows.