Yes, but you have to be connected to your August lock to do that. On that note, any modifications to guest access require you to connect to the lock. That's where having the August Connect is nice, but it's not neccesary.
When you're near the lock, go to the 'Guest List' page and select the user, then modify their temporary access as needed. For longer-term guests, I usually add a entry code (for the keypad) at the same time, and use the last four of their cell phone number so it's easy for them to remember.