Go to the Apple App Store and search for "SmugMug." Install the official app (blue icon with a white camera shutter). Note: Do not confuse this with "SmugMug For Photographers" (legacy). Use the main SmugMug app.
If you prefer a completely hands-off approach: smugmug auto upload iphone
Tap "Auto Upload" and slide the toggle to the ON position. Go to the Apple App Store and search for "SmugMug
Use this guide if:
per file) and set the app to only upload while the device is to preserve battery. SmugMug Support Key Features & Capabilities Full Resolution smugmug auto upload iphone