Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The top four placed teams from each group in the Segunda División B played in the Liguilla de Ascenso. Each liguilla contained one team from each of the four regular season groups. Teams were then drawn to plan one another with the 1st placed team in each group playing the 4th placed team, and the 2nd placed playing 3rd. The winners of these ties then played each other with the winning team being promoted.
The teams finishing 16th in each group of the Segunda División B were drawn into 2 pairs, with the losing teams relegated to the Tercera División.