Regardless, my question was more of a general one. What do you have to do programming-wise when you buy a chip directly
from the manufacturer and you want to use it.
As a general answer to your general question, generally you start first with a dev board like Teensy, or Arduino, or ST Discovery, or one of many others on the market. The path people generally follow first looks like "proof of concept" work, where you try to get the dev board to run some key part of your project. For example, if you're going to make a product involving a brushless motor, maybe you try using libraries and writing some code to make the motor spin at a certain speed. Generally this proof of concept work has little optimization. The general idea is to confirm whether you are able to get the key parts working, which involves the hardware capability, breadth of library support, and your own skill to fill in the needed pieces. This early work involves quite a bit of learning, both about the hardware and its software tools.
Generally "proof of concept" prototypes are built on solderless breadboards or by soldering parts on
stripboard or
vectorboard.
Generally speaking, what is *not* usually done is a custom circuit board as the very first step. In these modern times where chips have so many advanced features, and where software tools offer many powerful but complex features, starting "from scratch" before you even have a clear idea whether the hardware, its existing libraries, and dev tools will meet your needs is risky and usually wasteful. Generally you would get a "proof of concept" working first on an existing dev board. Then the next general step is to attempt your own custom board design, usually by copying some or all of the dev board's schematic and adding the parts you've used.