When viewing an image on Dwell you want to save, tap the heart button displayed on the bottom right corner of the image. The image will automatically save to the last collection you saved an image, and you’ll notice the heart button change to a checkmark button, indicating the image successfully saved.
A full list of your collections will display, and the collection you recently added the image to will be highlighted and indicated with a checkmark.
To add the image to another collection instead, add the image to multiple collections at once, or remove the image from its existing collection, simply check or uncheck each collection. You’ll also see the option to “Add a new collection” in the top right corner of the menu.