You missed it. Two ways. Either drag the event left or right for slower/faster speed while holding down Ctrl and you'll see a zig zag line through the event or right click on the event and add a velocity envelope with gives you a percentage so you can be more precise.

In my view the simplest way to have a freeze frame is either isolate just a single frame by zooming way in on the timeline or take a snap shot of a single frame then drag the image to the timeline. Either way you want a new event. Drag the event to fill the time space you want for a freeze "frame" which can be any length of time.