We got a couple of comments yesterday on our tip about using shared Photo Streams on iOS devices. One of them was how to add new people to a Photo Stream once it’s been created. It’s fairly unintuitive (Apple, are you listening?), so here’s a quick step-by-step on how to do so.
Launch your Photos app with a tap. Then, tap on the Photo Stream tab at the bottom. If you’re using an iPhone or iPod touch, tap the blue arrow next to the name of the shared Photo Stream. If you’re on an iPad, tap the Edit button, and then tap on the shared Photo Stream.
Next, to add a new person, tap the Add People… section below the list of other subscribers and either add a person from your Contacts via the little blue button, or just type in an email address. Then tap the Add button in the top right corner.
If you want to delete a subscriber, tap the name of the person you want to remove in the list of subscribers, then tap the big red Remove Subscriber button. Boom! They’re gone.
Subscribers can only view or comment on the pictures with shared Photo Streams, on their own iOS devices or on the web. Hopefully, Apple will add a way for subscribers to add photos to a shared stream, as well, which will make the whole thing much more useful for groups who want to share among themselves.
Source: iCloud Support