The picture must be uploaded on any website and you have to copy the link of the image, then you have to paste it in the image-url section on Musing. Musing will automatically detect the photo and display with your answer.

If you're using mobile, then 1st post the worlds simply, next edit and paste the url-link.

Note that, you can do attache a picture with question on Musing. You can't upload a photo  on Musing.