Here's part 1 of a 13 part Presonus Studio One tutorial which guides you through using the song page.

1. You can use the "Close" command to close any Song that is in focus. With the "Close" command (Ctrl + W) only the current visible Song is closed and Studio One will keep running / stay open. If you use the "Close All" command you will be taken back to the Start Page.

2. Even if you have one Song open and use the "File" > "Close" command PS1 will simply close that Song and take you to the Start Page.

3. If you use the "File" > "Quit" command (or the Close / X button for the whole Window...top right of any open application in Windows) PS1 will likely ask you if you want to save changes for each open Song before closing the application completely.

4. You can save a New version of your Song with the "Save New version..." command. This will place a new version of Song in the History folder for your Song. If you browse to your Song folder you will see a History folder there if you have saved a new version.

 5. You can drag this new version into S1's arrangement view and S1 will immediately load up that version of your Song.

Original source: here.