The title is the question. I have screenshots that make a question easier to understand than anything I can write.
You need 10 reputation to be able to post images. Until then we will be happy to edit your post to include your screenshot once you provided the link to it.
First of all, in your case the problem is your reputation. As a new user, you cannot post pictures. We will update the posts for you, until you gain the privilege to do so.
The simplest solution, once you can, would be clicking the
img button on the editing form, or using the shortcut it shows (Ctrl+G):
This then prompts you with another mask which allow direct upload and linking and thus automatically inserts the necessary code:
If you do not want to use this mask, however, you can click the
Images button on the help bar, which shows the markup: