This sample demonstrates how you can use popups to edit features in a feature layer.
Browse feature: Tap on a feature to display the popup. The popup may contain information about a number of features depending on the density of features at the tapped location. It lists the attributes and attachments for each feature. You can enable the editing mode by tapping on the Edit button. In this mode you can edit attribute values, change geometry, add or view or delete attachments or delete the feature. To exit the editing mode you can either tap on Cancel, which would ignore all the changes, or tap on Done, which would save all the changes you made during the edit session.
Add feature: Tap on the Add new feature in the bottom toolbar to initiate adding a feature. You would be shown a list of feature templates, already available. Picking one would open the popup for the new feature in the editing mode. You can use the geometry button the on bottom left to specify the location for the new feature. Once you are finished updating the attributes or attachments you can tap on the Done button to save the feature or on Cancel button to discard.