Photos need to be stored somewhere else online. A lot of members use Flickr but other services work as well.
Depending on the service you choose to store your photos, you'll need to get the url to the actual image.
Once done, return to Nelsonfoto and click on the "Insert Image" button in a new post or reply. This will put the following bits in:
[img][/img]
Put the url between the two IMG commands.
Example:
[img]http://www.some-website.com/some-image-name.jpg[/img]
Hit "preview" to make sure the image shows up and then hit "post" when verified.