Here's how I do it.
Click on "Go Advanced" lower right corner.
Top row of icons, far left, is an "A" colored in blue. Click on that turning off the "blue".
Place your cursor wherever you want the pic to appear in your post.
Second row of icons, fourth from right end is a square icon of a picture with black dots at the corners. Click on that.
A window will appear on the screen, I use "from computer" so click on that.
Then click on "Browse". This will take you into your computer to search for the pic you want to post.
Find the pic, select it, click on "open" at the bottom of the window. This will cause the "address" of your pic to appear in the space to the left of "browse".
Now click on "upload". It may take a few seconds for your pic to appear in your post.
The pic will appear in thumbnail size. If that suits you, continue with your post.
If you want the pic to be larger double click on the pic. A new window will open giving you choices as to the size it will appear in your post. I usually use "full size".
Once you have selected the size you want you are ready to click on "submit reply" at the lower right.
Bingo, you have just added a pic to your post, kinda like this.