Photoshop documents (.psd) cannot be directly loaded into Singular.
You can, however, export optimized images from Photoshop that can be used in Singular overlays. These images can be uploaded to the Singular Dashboard. They can be used for building custom overlays in Composer or for referencing in a Control App when operating the overlays live.
Remember .pngs are good for images with transparency and .jpegs are good for images without transparency. We recommend running your images through an image compression tool like tinypng to optimize your overlay playout.