There are two options to insert an image into your post:

Option 1: You can insert an image into a post by using the "Insert Image" icon on the top of the edit section. To insert the image you've uploaded in your account, click the "Insert Image" icon and then the drop down menu. Select one by clicking it from the list. You may also re-size your image by adding the height and width in the box.

You can also insert an image from other sites by entering the URL of the image in the "Enter URL" section. Afterwards, click the "Submit" button.

Option 2: Write HTML image tag to include the image in your post. Check here to see how to get the image URL.

If you wish to resize and adjust the position of the image, you may check here.