You can use Sparky Page Builder to edit Joomla articles, custom modules, and other Joomla content that uses an editor from the front-end of your Joomla site. Of course, you should be logged in and have the correct privileges to edit the content.
If you accomplished the installation and activation steps of the page builder, it will be set as a default editor for your Joomla site. For any input field where the Joomla editor is used in the front-end of your website, you can use the page builder.
In order to be able to change images on a page from the front-end, you must enable option Content > Articles > Options > Editing Layout > "Frontend Images and Links" in your Joomla Administrator's panel.