Well that depends on the hardware you have. For the most common sensors, drivers will exist that detect the device is connected and publish their data as a ROS message (i.e. rplidar, realsense camera). Similarly, for actuators there are packages like ros_canopen that are used when the hardware is connected through for instance a CANbus. I would recommend just searching for hardware online or looking into the turtlebot as an example. If you already have hardware and drivers don't exist then you will have to create the driver yourself. This usually comes down to writing code in C or C++ that reads and writes to/from a port on your board/computer and publishing the data as a ros-message or translating a the information from a ros-message to the hardware's protocol.

Thanks for the suggestion