There is just one women pro b'ball league and, to be true, it is only semi-pro. Only the foreign players and those in the richest clubs are able to earn the money enough for living. Its name is, surprisingly, Liga Femenina, and it is ruled by the Spanish Basketball Federation (as it is common in all sports in Europe). The Website (in Spanish only) of the Federation is
FEB It has 14 teams/clubs. Each of the clubs are allowed to have just 2 non-EU players in their rosters. I cannot say how they get to sign a foreign player, but I supposed that it is done through agents.