How to Choose Which Biome You Spawn In
Find and Open the Config File
After installing the mod and launching the game once, a file called spawnbiomes.txt is generated in your Minecraft config folder. Open it with any plain text editor. Inside you will see a list of biome names, each preceded by an exclamation mark (for example, !minecraft:plains). The exclamation mark means that biome is currently disabled as a spawn option.
Enable Your Preferred Biome
To allow spawning in a biome, delete the ! in front of its name so the line reads as just the biome name. Save the file and close it. The next time you create a new world, the mod will use your edited list to decide where you spawn. If you only enable one biome, you are guaranteed to spawn there.
Selecting Multiple Biomes
You can enable more than one biome. When several are active, the game picks one at random, weighting each enabled biome equally. Enabling two biomes gives each roughly a half chance; enabling more spreads the odds further. Keep the list short if you want a predictable result, or add several if you enjoy variety.
Applying Changes
Config edits are read when a new world is generated, so existing worlds are unaffected. Always create a fresh world to test your selection.