Technically, the emperor ordered the eunuchs to gather beautiful women from the kingdom and choose the best one to be his concubines. Although concubines of Chinese emperor are usually no more then his sex toy with no power at all, if they can make him feel good, make him feel happy, or give birth to a boy, they can be elevated to be the empress (if he didnt have one yet) or replace the current empress (only dumb emperor did this because it led to inner fighting between the relatives of old empress and relatives of new empress). However, emperor Ling was not smart and he spent his life playing around so it's easy for the empress/concubines to manipulate him into giving so much power to their relatives. In this case, he had already deposed the previous empress and killed her relatives, included her father.

However, being a butcher doesnt mean He Jin is poor or without connection. They only choose women with validated background, virgin, well-educated and mostly come from the powerful and rich households. He Jin family is not poor at all since He Jin family bribed the eunuchs so that they would let her become the concubines. And it has to a beefy bribe since it's obvious that He Jin family is not the only family to try to bribe the eunuchs.