Hover over the stream in the left sidebar.

Click the ellipsis () to the right of the stream.

Click Stream settings.

Select the Personal tab on the right.

Under Notification settings, toggle your preferred notifications settings for the stream.

Click on the gear () icon in the upper right corner of the web or desktop app.

Select Personal settings.

On the left, click Notifications.

In the Notification triggers table, toggle the settings for Streams.