Navigate to Job > Project Management > Schedule. Click the Phases button to show or hide phases in your Gantt Schedule.
ℹ️ You can also view this through your Schedule Tab.
Now double-click a Schedule Item or select the three dots alongside the item to open the Edit Schedule Item menu, where you can assign the item to a phase.
💡You can now choose to customise your global schedule view by clicking 
or 
schedule items in your Gantt format.
The schedule will remember your view, so when you return to an item, everything stays just how you left it.
See this article for further information on how to create a schedule item.