Use the Media & Text block to place an image or video side-by-side with text.
Get started by clicking the + Inserter icon 
at the bottom-left corner of the screen and select the Media & Text Block from the blocks list
After adding the block you will be able to add an media (image or video) and a text and you can also select the layout of the block, if you would like the image to the left and text to the right, etc
Once you add the image and your text it will look on the mobile a little different than it will look on your site. For example, you can see the option above selected show the media to the left and text to the right which is how it will be displayed on bigger screens.
On the mobile editor and on small screens it will show one under the other like this:
But on bigger screens you can see it displayed like this:
You can also click on the cogwheel icon to select the option to crop the image if you need to
