Import
Darkroom works directly with your Apple Photos library, so most of the time there's nothing to import at all — your photos are already there the moment you open the app. The cases below are for the times they aren't yet: bringing in shots from a camera, an SD card, or the file system.
From iCloud Photos, there's nothing to do
If you use iCloud Photos, every photo and video in your library is automatically available in Darkroom — no import step, just open and browse. A photo you take on your iPhone shows up in Darkroom on your iPad and Mac, and vice versa. For the full picture of how this works, see iCloud Library.
From a DSLR or mirrorless camera
When you connect a camera or SD card to your iPad or Mac, you import through Apple's built-in flow rather than a separate step inside Darkroom. On iPad that's the Photos app or the Files app; on Mac you can use Image Capture, the Photos app, or simply drag the files out of the card in Finder. Either way the photos land in your Apple Photos library, and Darkroom picks them up automatically — they appear in the Recents album as soon as they're in.

From Files
You can also pull photos in from the file system. On iPhone and iPad, use the file picker to browse and select from Files, or open a photo in another app and save it to your photo library. On Mac and iPad, drag and drop photos straight into Darkroom or the Photos app — they're added to your library and appear in Darkroom immediately.
However they arrive, imported photos join your Apple Photos library and show up in Recents right away, syncing to your other devices if iCloud Photos is enabled.
Supported formats
Darkroom supports the same image and video formats Apple Photos does — JPEG, HEIF, PNG, TIFF, ProRAW, and most RAW formats including DNG, CR2, ARW, NEF, ORF, and RAF for photos, plus H.264 and HEVC (H.265) for video. RAW support depends on your device and operating system version, since newer devices and OS releases recognize more camera models. The FAQ links out to Apple's documentation on supported RAW formats per device.