You can do it like this:

1. Method 1: Use an online tool to generate transparent circular pictures, cut the square avatar picture into a circle, and then save it in PNG format. Then place it on the circular background image.

2. Method 2: Use Photoshop software, first use the elliptical marquee tool to select the part of the square avatar picture that you want to keep, then press Ctrl+J to copy to a new layer, and then hide the original layer. Finally, save it in PNG format and place it on the circular background image.

3. Method 3: Use Photoshop software, first use the rectangular marquee tool to select the part of the square avatar picture that you want to keep, then press Ctrl+J to copy to a new layer, and then use the rectangular shape tool to draw Make a rectangle the same size as the background image and fill it with white, then hold down the Alt key and place the mouse between the two layers to create a clipping mask. Finally, save it in PNG format and place it on the circular background image.