Hi Vaiva,
If you can upload images to a cloud storage site like amazon s3, you can then upload these images to your user tours.
I was able to upload an image by pasting this into the content field of the user tour:
<img src="https://s3.eu-west-1.amazonaws.com/adapt.totaralms.com/Assets/C011_A020/C011_A020_55a.jpg" alt="" width="834" height="334" role="presentation" class="img-responsive atto_image_button_text-bottom">