power from below
What I understand from the term "Power From Below" is the power the lower class people have over people that are on the top part of the hierarchy, for example the Government over the citizens.
The power of the people above the middle and lower class people has usually always been because of money, health, gender and social classes. Obviously a poor person is not going to be as powerful as the CEO of a big electronics company but that can change if there are more poor people against the CEO of the big electronics company.
An example is when women wanted to vote. It was a matter of gender discrimination where men were more "powerful" over women because women were only there for having and taking care of children and the house. Since they wanted a change, a lot of women had to unite together and speak as one which after a lot of battles and commitment, managed to make a person like me to have the right to vote (although discrimination against women still exists till this very day!).
To have power from below so that you get your voice above, usually requires money. An example can be seen from Vincent Van Gogh. At the time, his art was not appreciated by everyone and he had only sold two paintings in his life with the help of his brother, whom funded and believed in him constantly.
Any type of election is power from below. People decide whom to vote to represent them and give them a voice or a better life, even though at times the wrong people may be elected.
Although there could have been be a lot of effort put into any type of protest, petition or wars, it is persistence and will-power that will lead you to a satisfying result!