After you Upload an Image or Photo,
You can use Image browser on the right side menu to browse the image,
Image will be in different different size.

If you are want to add the image to Topic/Context just drag and drop in text area.

If you want to add the image to Comment/reply, please right click on the image, go to property and copy the URL of the image
once you copy URL of the image use it as followings

<img src="URL" width="450">

Add the above code and replace the URL with image URL you have copied and post.