To crop a photo on your Mac, you can use the Photos app. Here are the steps:
1. Open the Photos app on your Mac.
2. Select the photo you want to crop.
3. Click on the Edit button and then on the Crop button.
4. Drag the corners or edges of the crop frame to suit your needs.
5. If you want to save the cropped photo, click Done.
6. You can also crop manually by dragging the selection rectangle to enclose the area you want to keep in the photo.
You can also use other apps such as Preview to crop photos on your Mac. Here are the steps:
1. Open Preview and click on File > Open.
2. Navigate to the image you want to crop and click Open.
3. Click on the image at a point you want to be a corner of the cropped image (if you want the cropped image to be square, hold down the Shift key).
4. Click on the Tools menu and select Crop or press Command+K.