After you log in, and navigate to the screen where you write your post, you will see this form:
Place your cursor in the location within the text you are writing where you want to insert an image. Then click on the tool highlighted with a pink circle above. When you do so, you then will see this screen:
Click on the BROWSE button and navigate to the image on your computer you want to add. Then click on the UPLOAD button. After you do that, you will see this screen:
You can use this tool to resize your image and place it left, center, or right, and can add a caption. IMPORTANT: Ignore the SAVE ALL CHANGES button. When you are ready to insert your image, click on the INSERT INTO POST button. That will take you back to the publishing form, which should show your image inserted within the remarks you are authoring.