Creating a Mod Menu is all UI work. You’ll have to create a button, that will open a options view controller. Once you have a stable menu, you’ll have to add the functionality to patch offsets, hook functions etc.
then all you have of to do is add your features.
Note: before you say I didn’t answer your question, I did. You asked how to create a Mod Menu, which is in the end a GUI with functionalities.
if your actual question is: ”how do I create a hack?”, then you should look into the tutorial section, after all it’s pure trial&error in the beginning & you’ll need the right motivation.