How can I tag photos received or saved on iPhone?

The only way to tag photos on an iPhone is to open the photo to view it enlarged and then to swipe up to see the details below the photo. Tap the Info button. There you can enter a description and add a location or adjust the date.

See: Edit photos and videos on iPhone - Apple Support (CA)

Change the date, time, or location

You can change the date, time, and location that’s stored within the photo or video’s metadata information. See See photo and video information.

1. 1. Open the photo or video, then tap .
   2. Tap Adjust Date & Time or Adjust Location.
   3. Enter the new information, then tap Adjust.

To change the date, time, or location of a batch of photos, tap Select, tap the thumbnails you want to change, then follow the steps above.

You can revert a photo or video to its original date, time, or location. Tap , tap Adjust Date & Time or Adjust Location, then tap Revert.