We get this question from time to time, and it's understandable if you've never seen a forum layout like this, so here's a quick guide on how to post an image in a thread or new topic on Permies.
Posting an Image with the 'Img' Button
First, where is the picture you want to post? In order to post an image in a thread with the img button in the menu, the image needs to be online somewhere.* You can upload your image somewhere, and then use that image address to put your photo into a post.
To add the image to your post, right click the full sized image, and select 'Copy Image Address'.
Go back to your post, and click the img button.
When the little window pops up, paste (or Ctrl/Command + V) the image address into the box, and submit.
It's always a good idea to make sure your post looks right before you submit it - check it beforehand with 'Preview'
**Note: If posting images from other sites, please make sure to include a link to the source below the image, and note that not all photos are free to post elsewhere. You can search for photos based on usage rights on Google Image Search by selecting Tools -> Usage Rights -> Free to use or share from the menu above image search results.
Posting an Image as an Attachment
If your image is on your device and you don't feel like uploading it anywhere online, you can just attach it directly to your post.
Write out the body of your post.
At the bottom of the post, you'll see some tabs - click on 'Attachments'.
Click 'Choose File', and select the photo you would like to upload, keeping in mind the file name will be visible to everyone.