Examine the app UI. Break it down to its own functionality. Use SRP (Single Responsibility Principle) making sure that each has its own single reason to change in a component.
Render html using a static props, passed down the hierarchy of the components.
Figure out what data in a component should be stateful. These data are represented in the app as props.
Know which component owns each piece of state. Usually a state is subject to how its parent component functions.
Initialize a hardcoded states to whichever component it lives.
Pass down event handlers to the hierarchy of components as props. Call those event on child level component to make changes to states whichever component is owning it.