How to Attach Image Window to Photoshop

As shown in the screenshot provided, my images are unattached to Photoshop and are able to move independently. I can still edit my images, it just is frustrating to deal with at times, as I'm used to the images appearing as tabs. I had tried dragging and attaching it (like you're able to do with the toolbar, etc.) but the blue halo that indicates it can attach the window isn't showing up. If anyone is able to tell me how to correct this, that would be great, thank you in advance!