Take the iPhone 8 as an example. The specific operations include the following steps:

1. Open "Photos" on the desktop of the phone.

2. Then click "Edit" in the upper right corner of the "Photo" that needs to be operated.

3. Click the "More" sign in the lower right corner.

4. Select the "Mark" option to proceed to the next step.

5. Click the plus sign in the lower right corner, select "Text", and then a text box will appear on the icon.

6. Finally, click the "Text Box" and select the "Edit" item, enter the text to complete the operation.