Open the image in Photoshop
Select the layer containing the image
Choose the Quick Selection Tool, Object Selection Tool, or Pen Tool
Select the subject you want to cut out
Click Select and Mask if needed to refine the edges
Adjust edge settings as needed
Output the selection as a Layer Mask or New Layer with Layer Mask
Use the Brush Tool on the mask to clean up any remaining areas
Save the file as a PSD to keep the cutout editable
Export the image as PNG if you want a transparent background