To add a picture to your Solid profile:
- Go to your profile (In my case this is https://teodora.solid.community/profile/card#me)
- Drag the file with the picture you want and drop it onto the blank profile image.
Note: In my case, I added a second picture and then had to delete it. To see How to deleted a resource in your Solid account see: https://github.com/solid/userguide/blob/master/README.md in the part Deleting a file.