I thought it was weird too at first.
When your project name in the project list on the left is selected and you’re in Project View, made sure you’re on the Properties tab.
Now click the ‘Add Sub-project’ button as many times as you need to create the right number of subprojects.
Then you have to click the plus sign to the left of the project name on your project list
Click on the Sub-project’s name. This brings up the window where you can edit the info.