The whole app is under Active development (The reason I haven't put an installation way, but if you know how to install the app, please create an issue when you encounter bugs in it)
At this point the app will create a text file to store the Tasks, I haven't programmed the file to be created in %localappdata%\Todo-Boi but, as soon as I have enough time, I will. Right now, the file will be created at [User], (just write your username at File Explorer)