How to build a kernel?

Question

linux

I have a device - Cowon Q5w.
It has a processor from RMI AU1250 MIPS technology.
Windows CE 5.0 is on board.
I wanted to install at least any Linux on it out of purely sporting interest.
I found a kernel on the Internet, patched its UART port in a hex editor and launched it through LoadlCE.
Clearly, the stump started loading and then everything fell into a panic kernel due to the fact that the files should be in NAND memory (which I don’t have) and I have them on the HDD. I don't know how to change.
Therefore, I want to ask you how you can collect the kernel yourself. Preferably a manual for full dummies.
I found this on the Internet , but I don’t know what to do with it