Any observation, photo, diary, activity, or milestone entries can be added to the portfolio. The entry can be added as soon as it is created, or after it has already been saved. If the entry has already been saved, edit the entry by tapping on the entry in the entry list, then choose the 'add to portfolio' option and re-save the entry.
On the mobile app
For Activity, Diary, Milestone, and Photo entries, tap on the Share button at the bottom right of the page then choose 'Add to Portfolio' and save.
For Observation entries, check the 'Add to Portfolio' option at the middle of the page.