You don't "generate" them from the keyboard. Three dots is an ellipsis. And certain word processors (like Word) will auto-correct the three dots into an ellipsis character (Unicode 2026). This is a typography artifact and NOT relevant to PowerShell. Type three periods.
In a document, if you intentionally wanted to insert the single-character ellipsis, you could use their character/symbol dialog and find it. Or you could enter Alt+0133 (the 0133 must be entered from the numeric keypad).