I
To save a post to a collection, press and hold on a saved photo, and the option will be given to add it to an existing Collection, or to start a new Collection.
Since last December, when Instagram first added the ability to save posts, several features have been added to the Instagram app such as the blurring of sensitive content, the ability to share multiple photos and videos in a single post, and the addition of Geostickers to Instagram Stories.
Collections do bear a similarity to the premise of Pinterest, which is based around the sharing and cataloguing of images and videos into boards known as "pins". It is worth noting that while pins on Pinterest are public, Instagram"s saved Collections are currently private and cannot be shared with other users.
The ability to save posts to Collections comes as part of the latest update to the Instagram app for Android and iOS devices, which is currently being rolled out.
Source and image: The Verge