First add one or more photos to a footprint. If a photo has date and location information, you'll see two small icons with the words "location" and "date" on each photo thumbnail, in case this meta-data is not available, you won't see the icons.
To use the date and time or location of a photo for a footprint, simply tap the photo. In the upcoming menu choose Use photo date and time or Use photo location to either use the date and time or the location for the entire footprint.
This is especially helpful, if you're retrospectively adding a footprint, no matter if it dates back a day or a year.