To slide a scene, you need a video editor and a video. I use DaVinci Resolve as the video editor because it's free and pretty decent.
In short, you're basically going to crop the video to an aspect ratio of 225x350 and keyframe the horizontal position of the video.
Step 0: setting up the project in DaVinci Resolve
Open Davinci Resolve and make a new project, name it whatever you want. Press Shift+9 to open your project settings, and adjust your Timeline resolution to the resolution of your video. Hit save and then go to the Edit
tab (located at the bottom). Press Ctrl+N to make a new timeline (name doesn't matter). Press Ctrl+I to import your video into the editor, or you can also drag the video file into the editor. Once it's imported into the editor, drag it onto the timeline.