Norton transformations
Beside the Thévenin circuit there is also a Norton circuit for simplifying a circuit. The Norton circuit is a current source in parallel with a resistor. In order to get to that circuit we can just simply do \(I_{norton} = dfrac{V_{TH}}{R_{TH}}\).
This is all I’m going to say, because the two circuits are equivalent to each other, use whichever circuit you like.
The main reason you should focus on Thévenin is because voltage sources are much more common in real circuits, so using a Thévenin equivalent circuit is preferred.