The Inventory Engine comes with its own Input Manager, to avoid clutter and separate it from the rest of your input management. Of course you can also decide to implement input differently, and call its various methods directly from your scripts, but this just makes it autonomous and ready to use.
Usually placed at root level on top of the dedicated Inventory Canvas, the InventoryInputManager component will require you to bind it to an inventory group, that will get shown/hidden when you press the open/close keys. Usually you’ll want to put inside that group your main inventory and inventory detail panels. There are examples of that in the PixelRogue demos. You’ll also need to bind (via drag and drop) your Inventory Dislay and an optional overlay to show/hide between your scene and your inventory GUI for better readability.
You’ll then need to decide whether or not you want to hide your inventory container on start (hiding it even if you’ve left it visible in your scene view), and whether or not you want to authorize inventory input only when it’s open (which is usually the case).
The last thing you’ll need to do is, for each action (move, equip, use, equip or use, drop, next inventory, previous inventory), specify what key bindings you want to use. You can specify an alt binding for each, allowing you to support keyboard and gamepad at the same time. All inventory panels are mobile ready so they just work via touch by default.