Menus
From the OverView menu you can set the tasks you want your colonists to perform, some colonists will not be to access all skills. For example nobles can only access research and firefighting whilst a settler can access all skills.
It is possible to get your base working very efficiently by managing who does what job, hover only the skills square to see a score out of 15. This will help you decide who you want doing each task. Using the wrong people will slow down your base. It's a good idea to study your colonists skills and apply them to what they excel at.
In standard mode, colonists will either perform a task or not, with tasks being ranked of greater importance the further left on the grid they are. In manual mode, each colonist's tasks can be prioritized from 0 (blank) to 4. 1 is the highest priority, 4 is the lowest, and blank tasks will not be performed. Properly utilizing manual mode can make sure everyone always has something to do, and avoid idle colonists.