To set up PVSNESlib, follow the Wiki, it's very well done: https://github.com/alekmaul/pvsneslib/wiki/Installation-with-Windows
For code editor, the Wiki suggest Programmer's Notepad: https://www.pnotepad.org/
Personally, I generally use Scite; https://www.scintilla.org/SciTE.html
If you never programmed in C though, you should be prepared to spent some time navigating the "oddities" of the language. It's very a powerful language, but it also require some "good habits" to avoid nasty bugs. But don't get discouraged / overwhelmed by the apparent complexity of C. To make a simple SNES game you don't need to master all the language features (for example, if pointers seems hard to grasp at first, you can make a game without them). And the more you code in C, the more natural it'll be :).
Great that you got the whole thing set up, that's the first step!
If you never programmed in C, I really recommend you to read books / websites / video tutorial about how to code on the language as the next step :).
To answer your question, you can (and will) write code anywhere is the file (more or less). The gameplay code will most likely go after the "put code here" comment. But when you want to use a variable, you'll have to declare it first, so you'll most likely declare the variables after the "#include <snes.h>" file.
If you trip on color restrictions or audio restrictions, you'll usually see it when running the game on emulator: nothing will show, or the color will be wrong, etc. (retro game development is usually quite scare when it comes to debugging tools :p)
Regarding input, PVSNESlib is quite nice as it accepts:
- BMP for graphics (be careful of the color palette, it needs to have 256 color palette BMP with only the first 16 or 4 colors defined depending on the graphics mode you'll use - usually it'll be 16).
- IT (Impulse tracker) for music and sound effects, if you use the "non-streaming" function. I recommend OpenMPT as a program to create those music and audio files (it's arguably the best "modern" tracker program available) https://openmpt.org/
- WAV for sound effects if you use the streaming functions (beware, it does work well only on NTSC, and it's quite complex to use - I recommend sticking to IT file for beginning)
You can open the source code of Keep SNES alive to see an example of that, the archive contains everything: code, images, sound, music, etc.
But as I said, you should really start by learning how to code in C first, else you'll have an hard time doing anything meaningful. You don't need to take a full course, but at least to learn the "basics" (using and typing variables, loops, creating functions, etc.)
You'll need to modify those file along the way when you'll want to include graphics or audio:
- Makefile: this file contains instructions on how to compile the game into a valid SNES rom. Depending on your project, you might have to modify it to include the name of the graphics files / audio file to include into your project.
- data.asm : this file list where all the data (graphics, audio, tilemaps, etc) are going to be stored in the ROM. Basically a SNES rom is a combination of several "slots" (or "banks") of 32kb. This file is used to define what data goes were, and will have to be modified each time you want to add a new asset into the rom.
- hdr.asm: this file is the "rom header". The only thing you'll need to modify in it, is the game title, all the other params are OK for most projects :)
Regarding Makefile, I suggest you to read tutorial / watch video about how to use them too, as it's a common topic in many programming projects :).
The other aspects are specific to the SNES and PVSNESLib, and you'll find more details about them in the Wiki:
https://github.com/alekmaul/pvsneslib/wiki/Sprites
Actually, once you're more familiar with C, I suggest you to follow the tutorial steps from the wiki:
https://github.com/alekmaul/pvsneslib/wiki/Introduction
You'll learn how to display text and sprites on screen.
