You can assign a career to a lot by clicking on that lot, selecting 'Zerbu' then 'Ultimate Careers' then 'Add Career or School', select the career or school you want, and select an existing rabbithole that contains that career or school.
The mod scans the Sim's interaction queue, and increases performance depending on which interactions are being used. The end of career rabbitholes is here! With Ultimate Careers, instead of going into a rabbithole to work, Sims will spend the work day at a community lot, doing work-related interactions - or slacking off.