To edit an image on the site, you would head to our design area BlockLab.
Once you head here, you would select the image you wish to edit (you should see a green highlight around the image appear).
Along the top of the page you will see a toolbar, on which there will be a box with the name "Effects".
Click here to add either "Fade Up (Once)" which will do the effect as soon as the image is shown on the site, or "Fade Up (Repeat)" which will do the effect every time.
See a screenshot below of the relevant area.
Make sure to publish the page to see the change on the site.