Depending on the situation, both methods can be very useful. Here are steps for both methods
Method 1 - Start from Scratch
Go to the Home Panel and scroll until you see the Other streams section. Then click on the plus button to create a new stream
You will then be prompted to create a stream as usual and adding a name and description (optional). There is just an extra step to add the people who you would like to share the stream with
Method 2 - Convert an Existing Stream into a Shared Stream
To turn a stream into a shared stream, first find the stream on the Home Panel under Other Streams.
Once that stream is selected, click on the Share button in the upper right hand corner of the stream.
Add the other users to the stream.
Then you should be all good to go! View the stream in the Others section of the Home Panel