Two methods to start a scanning session.

• Selecting the session button on the bottom left in the Main View
  Tap + and enter a session name.
  You are returned to the main view.
  Tap the round "Take Photo" button to start capturing your 3D object.
• Tap the round "Take Photo" button in bottom center of the main view.
  The first tap after starting the app will bring up the session name input.
  Enter a session name.
  You are returned to the main view.
  Tap the round "Take Photo" button to start capturing your 3D object.
  

If you use the name of a prior session, that prior session is deleted.

To add photos to a prior session, make two sessions. Then on the Mac combine the two folders.

See the photos taken during the current session or previous sessions by selecting the photos button on the bottom left in the Main View.

In the sessions view tap the Folder icon. Slide the folder to the left to reveal the delete button.

By default the session is in Manual. Each click of the photo button will record one image.
Tap the "M" button to toggle to "A" for automatic mode. In automatic mode, one photo will be take every few seconds.
Continue photos until there is at least one complete circle around the object. Experiment with the number of photos, 50 or more may be required for one rotation.

A small automatic or manual turntable and a tripod to hold the iPhone/iPad will produce the best result.
The more photos the better the result.
Diffuse lighting without bright reflections works best.

If the object has few distinctive features, try putting scanner reflector dots on the turn table in unique configurations. This will give the scanner unique clues for aligning all the photos.

To scan the bottom of an object, do all sides first. Then lay the object on its side with bottom toward the camera but in the same relative orientation from the last photo. Continue photos with another 360 set of photos. Normally the last bottom set of photos will require fewer photos in one rotation.

Connect your iPhone or iPad to your Mac with a USB cable or share with AirDrop or iCloud.
The finder will show your device. Select your device in the finder, then select the Files item, and finally select the Scanneя app.
Your scanned items folder with appear in the finder window.
Drag your scan folder to your Mac and use the Modeleя to create 3D models.