To update the status of an Item, you can do this from either the Item itself, or in bulk from the Content tab:
1. Open the Item you want to change the status of
2. Click on the status dropdown
Choose the new status you'd like the Item to have.
3. Loop in anyone you want to notify of the status update
People assigned to the Item will be automatically looped in by default, and you can loop in anyone who isn't assigned to the Item by clicking the 'Loop someone in?' link (note: this doesn't assign this person to the Item, they're simply notified of this status update). You can then add an optional note to the notification sent.
4. Update the status
You can send a note to anyone being looped in.
You can also update the status of Items in bulk from the Content tab:
1. Head to the Content tab
2. Select the Items you want to change the status of
3. Select "Update status"
4. Select the status you want to change the Items to, and click "Update Status"
You can choose who to loop into this status change. This will display everyone who has access to the project.