First, make sure your timeline isn't wrapped. For some reason, clip speed adjustments are not available if you're using a wrapping timeline. To change that, go to View in your top menu bar, and make sure Wrapping Timeline is not checked.
Once that's done, you can change the clip speed. (I find that if I was using a wrapped timeline, once I change it I have to click on another clip and then click back to the clip I want to change. Otherwise, the option still won't show. Weird, I know.) Right above the video player, in that toolbar of options, you'll see one that looks like a speedometer. Clicking on that will open the clip speed options.