Bears den from November to April. If the bear is a female there may be small cubs present, which can complicate the solution. Ideally (for the bear), minimize disturbance of the bear and it will leave on its own in due time (March/April). If you want or need the bear to move on before spring, make loud noises and/or use lights. Maintain a safe distance. If there are small cubs present, the sow (female bear) will need time to locate an alternate den and return to remove each cub. You should notify your state wildlife agency in this situation.
If the bear does not leave and you cannot tolerate its presence, then trapping and moving the animal should be considered. Contact your state wildlife agency to assess the situation and take appropriate action.
After the bear(s) have left the site and you are positive it/they are not returning, close the entrance to the den with rubble (rocks, logs, etc.) to prevent wildlife access to the site. Bury the rubble under at least 12 inches of earth to deter animals from digging back into the den.