To insert an image click on the 'mountain icon' in the WYSIWYG bar. The insert image (and video) pop up window will appear.
If the image/video you want to use is already on the site, navigate to it using the left hand navigation. Alternatively you can choose to upload an image/video using the upload image button.
Once you have located/uploaded the image/video select it by ticking the radio button or clicking on the thumbnail of the asset.
Click ‘Continue’.
Select an insert option from the list (note that video options will only display relevant to videos):
Depending on which insert option you choose you may be able to further adapt your image by adjusting the width, height, crop etc. and click 'Continue'.
Once you have input your options, select 'Continue'. You can then change the image alignment by selecting 'Alignment'
You can also increase the height and width by selecting 'Show advanced' and inputting percentages so that the image is responsive to the size of the cell/block (space) it's being inserted to:
Once you're done, select 'Insert'.