: In principle, copy and paste should work as well. However, not many apps support Android's clipboard for images (LectureNotes does).
What definitely works is to to share the image and to select LectureNotes as recipient. Then, LectureNotes will come up and either (1) ask you to open a notebook to import the image into or (2) directs the image import into the currently opened notebook. Whether (1) or (2) occurs is decided by the option `import image in open notebook´ in the app's import settings.