Creating a new world is the safest and most reliable way to use any add-on:
Go to the tab, find the corresponding pack, and activate it.
The Jenny Mod is a popular modification for Minecraft Bedrock edition, designed to enhance gameplay and provide new features for players. For those unfamiliar, Minecraft Bedrock is a unified version of the game that allows for cross-platform play across various devices, including PC, Xbox, and mobile.