What is "enrolls"

Usage examples of "enrolls".

He enrolls as a scout at Fort Tuscelan, the last Aquilonian outpost on the east bank of the Black River, deep in Pictish territory.

Then Brian, now the dishy Diane, enrolls at Georgia State - honors computer science major, by the way, which explains the high-test firewalls on the e-mails she sent to Grace.

Do you think we impart all we know to every young dullard who enrolls in the Academy, or is it likely we hold greater, deadlier mysteries in reserve?