Notice: This is for iPhones.
Step 1: Locate and open the App Store
Step 2: Click the Magnifying glass icon
Step 3: Type Duo in the search bar > click the Search Icon
Step 4: Locate Duo Mobile (shown below)
Step 5: If you see Update in a blue bubble, click Update (shown below)
After clicking, the app will update.
Note: If it says Open in a blue bubble, then it’s already up to date (shown below.)