I am trying to book an uber ahead of time but cannot seem to figure out how to.

Likely not supported in your city/location. Only available in certain cities.

Did you follow the instructions in this article?  Give it a try:

How To Schedule Uber Rides in Advance

Next, you want to make sure that your Uber app is updated and is the latest version.

If you still do not see the options as outlined in the instructions, it is possible that Scheduled Rides is not available in the city, or at least in the area you are trying to schedule a ride for.

I am also including a screenshot that shows the icon you need to click on.  It's the car icon with a clock next to it:

ippei 1202

Uber Driver, CEO of TaxiFareFinder and Unleashed, LLC