It depends on what they mean by "add videos". If they are talking about inserting a video onto a page from external sites like YouTube, the in-editor button to import videos is gone. They will have to use the "add video" button on Special:NewFiles before editing the page. If they are talking about inserting video files from their device, they should be able to upload those with the in-editor upload tools. They should be aware that only a few video formats are supported but I believe the new platform is actually more permissive than the old platform was. Either way, once the video has been uploaded/imported, they should be able to insert it into the page using the same media insertion tool used for images. Just search for the video name and it should show as an option.