People become licensed through training and/or passing an exam. In many cases, an individual must complete certain steps, such as the completion of an educational degree in a particular area of study, before becoming elligible to attempt licensure. Individuals sometimes advertise their licensed status by appending an acronym to their name: Jane Doe, CPA.
Licensure may be perpetual or may need to be renewed periodically. It is very common for renewal to depend in part or whole upon evidence of continual learning--often termed in the US continuing education or earning continuing education units CEU.
Licenses are generally offered within jurisdictions which are usually a state or territory. This creates interesting problems. Jurisdictions may have wildly varying requirements for attempting or achieving a license. For some licensees, it is hard or impossible to move their practice to a new jurisdiction and obtain licensure in the new jurisdiction. And there are questions of jurisdiction: If a doctor provides medical advice over the Internet to an individual in another jurisdiction, is she practicing licensed medicine in her jurisdiction or unlicensed medicine in the patient's jurisdiction?