To use the datapack, generate a world with cheats enabled, then do /reload,
And you are done!

To enter the snow dimension just step on a pearlscelent frog light. That's the purple one.

Once you enter the snow dimension you are on a 1x1 bedrock platform. You can't build on this platform.

If you want to respawn in the Snow Dimension, do /setworldspawn so that everyone that joins your world will (re)spawn there. Or use a respawn anchor.

In the snow Dimension, it is always day. Beds will explode, but you can use respawn anchors. You can find strongholds, mineshafts & dungeons.

You can't make nether portals in the snow dimension.

To get back, stant on a Verdant Froglight block. It will teleport you to the overworld.

(might be in the sky so watch out)

That's all the info, have fun!