Premiere has a lot of options that all interact. Please, first ask the lab assistant to help you before changing the settings.
Cleaner is the subprogram that runs to export clips and stills. Cleaner normally runs without any problems, but exporting always takes a long time. If Cleaner won't open when you try to export, it means that too many things are open and Cleaner doesn't have enough memory. Click on the icon in the very top right of the screen and close all programs that you are not currently using (normally everything except for Finder and Premiere).
Also, please note that because Cleaner is a memory intensive program, working with other programs on the computer while it's running will slow Cleaner down.
To make sure that audio and video capture work independently and together, all of the settings for the project and for the capture need to be set correctly. The default settings will capture both audio and video as they are, but many people use the lab and so settings often get changed. The screenshots on the settings page shows how the project and capture settings need to be for audio and video capture to work at the same time.
Please ask the lab assistant for help when changing any of these settings.