From the "My Day" screen go to "More" on the lower right corner. select "Activity Statistics" in the top. Under "Activities" u find "Add Manual activity"
I contacted Garmin Support about not being able to manually add activity on the iPhone app. This is their reply:-
Thank you for contacting Garmin International.
I would be happy to help you out with this. The app development team has been made aware of the issue and are working towards a resolution. I apologize for the inconvenience. Please let me know if I can be of further assistance.
Ever since the update on both my Vivofit2, and the Mobile App. I cannot get activities to sync at all. Also, steps are showing up short, the device will say 13000 and both PC and Mobile App say 12800. AND, MyFitnessPal is not syncing correctly. I've removed the Vivofit from Garmin Connect and the Mobile App and paired back to both, no results. As far as MyFitnessPal, I've disconnected in both the app and Connect, then reconnected to no avail. All was working as it should prior to this UPDATE. I sure hope there's a hotfix coming really soon.