Edit->Project Settings->Editor Perforce Greyed Out

Edit->Project Settings->Editor

Version Control Mode

The Perforce option is greyed out. Why? Only Visible and Hidden Meta Files options are selectable. I have perforce installed and the new project is located in my workspace (all files are marked for add). What am I missing??

Its Pro only feature:
Version control integration (Unity Pro Only)

You can find more differences between free and pro here.