Need help uploading photos to a private message

Hello. I am trying to figure out how to send photos in a private message. I have photos on my computer desktop that are ready to send but the private message tools only show an option to send a photo if it has a url... Since the photos I want to send are not on the web they do not have a url. I have tried to paste my photos into the pm but it isnt an option. I have also tried to paste in the address of the photo I want to send using the local address instead of a url but that isnt working.
How does one send a photo in a pm?