I show my pictures by linking to them at Flickr. Flickr likes you to post your picture such that people can click on it and go to the picture's page at Flickr. Here's how you can do that.
At Flickr, on the photo's page, click the curly 'share' arrow, below and right of the picture. This opens a window where you can choose what size you want to show the picture. When you've chosen, copy the code in the upper box.
Now come to photo.net. Paste the code in the edit-box at the bottom of the thread you're posting to.
Insert a line above that, and type [img][/img]
In the code you copied from Flickr, select the URL of the image itself; that's the URL following 'img src=' in the code you brought from Flickr. The selection should start with https: and end with .jpg. Don't include the quotation marks. Drag this URL to between the img tags.
Now select the other URL, following href= (as above: everything between the quotation marks, but not the marks themselves), and copy it.
Select the whole top line [img=https:.......jpg] and then click the 'chain' icon above the edit-box. This opens a little window. Paste the URL into there, and click 'insert link'. The little window will close. In the edit-box, you will see the top line is now grey.
Now, you can delete all the rest of the code you brought from Flickr. Add any text you want to appear with your picture, and post it.