Two ways:
Elections
or
Direct public input to their representatives via phone, mail, email and public political events.
The kingdom went into decline from the mid-16th century CE when the Portuguese, put off by the interference of Kongo's regulations on trade, moved their interests further south to the region of Ndongo. The latter kingdom had already defeated a Kongo army in 1556 CE.
A. to help America get through the great Depression. Hope you find this useful