I'm trying to start making custom world generation but the wiki article isn't being of much help

The first thing the wiki article on custom world generation (https://datapack.wiki/guide/worldgen/custom-worldgen) talks about is Dimension Type. It shows a file dimension_type/overworld.json with this content:
{
  "ambient_light": 0.0,
  "bed_works": true,
  "coordinate_scale": 1.0,
  "effects": "minecraft:overworld",
  "has_ceiling": false,
  "has_raids": true,
  "has_skylight": true,
  "height": 384,
  "infiniburn": "#minecraft:infiniburn_overworld",
  "logical_height": 384,
  "min_y": -64,
  "monster_spawn_block_light_limit": 0,
  "monster_spawn_light_level": {
    "type": "minecraft:uniform",
    "max_inclusive": 7,
    "min_inclusive": 0
  },
  "natural": true,
  "piglin_safe": false,
  "respawn_anchor_works": false,
  "ultrawarm": false
}
I tried recreating this file and changing some of these parameters but nothing is changing. I have no idea what to do now. Can someone help?