It’s like playing 3D Tetris really. Always place large heavy items, or items you will not need access to, at the rear of the unit and work towards the front with more fragile items, or items you think you’ll need to get to while using the storage.
You are paying for the whole space including the height of the storage, so it makes sense to store items in an upright position like beds, couches, rugs, and consoles. Don’t forget to use blankets or cartons as padding. You can also use shelving if you like.
Always pack boxed items with each other, ideally with the same size, and put soft furnishings and items that do not weigh very much on top, yes it can be your bicycle. Once you have a solid foundation. Lastly, cover your belongings. If you are going into all the trouble of storing them, then pack them well.