If you want to put up shelves, pictures etc this is fine – just b aware that any holes in the walls will have to be put back to the way they started before you move out – otherwise this will come off your security bond.
If you want to change the layout of the room (adding partition walls), we will work out the plans with you then get quotes for the works to add the walls. The works will be chargeable and will have to be put back to the original configuration if you move out.