First, as others have said, you need to put him in the correct area for his job.
there are three career areas, the workshop (for hands on making things), the kitchen (for cooking related things) and the computer room (for office related things).
For each area you sort of need to find a "sweet spot" to drop your peeps on or drop them in the room repeatedly until you get "working on career."
I found that the Kitchen career you need to drop the person in the upper right of the kitchen (to the right of the sink) seems to work best, in the office, dropping themn on the center of the desk between the two computers seems to work best, and in the workshop, on the table on the top of the room seems to work best for me- your mileage may vary.
You should also "praise" your peeps when they work, as this will make them like working and want to work more. Keeping them happy seems to help with how often they want to go to work on their own.
Note: females carrying young babies do not like to work, so don't expect them to work at that time.