No, you don't need the insert media button at all. What you'll do is set up your photobucket account first. Its free and easy. Familiarize yourself with uploading photos to it which you can do via their interface, or you can even email photos to your account.
When you click on a photo in Photobucket you'll see on the left hand side, several codes that will allow you to "share this image". You'll have to click on the one that says IMG Code and it will automatically copy (like ctrl c). Then you would open a post or reply, such as this, and then paste (ctrl v) the code into your post.
Don't be alarmed. When posting the code will still appear, you won't see the actual photo until you've submitted the actual post.
Hope that makes some sense. Its not as complicated as I've probably made it sound.