Instagram finally released the feature to manage and add more than one account on Instagram app for iPhone and iPad devices. To add multiple Instagram account on iPhone and switch between accounts, do as follows:
1. Open the Instagram app on your iPhone (Make sure you have updated the Instagram and it is running on version 7.15 or later
2. Tap the Profile button in the bottom bar (it is the last one)
3. Tap the Gear icon on the top right of the screen to open the General settings
4. Now, scroll all the way down and tap the Add Account option
5. There you can easily add another Instagram account and add to your already existing account. (do this again, if you have more Instagram account to add)
To switch between different Instagram Account, just do these simple steps:
1. Go to your Profile (Tap the Profile icon in the bottom right)
2. Check the top of the screen, and tap your Instagram User name.
3. Now all your added Instagram accounts are shown and you just need to choose between them to switch.