You don't. Way back when it first premiered you used to be able to connect more to the iPad using the USB port on the camera connection kit. but a 2011 update lowered the power sent to that usb port, rendering many of those devices useless.
Joystick and cabled keyboard will not work. A bluetooth keyboard will.
External hard disk will not work. In addition to the power issue, the iPad has no file manager system, so there's no support for the transfer of data to an external device.
There are some USB sticks that will work, but I've literally had a 50/50 success rate. and the only protocol for import that's supported is to pull images and videos from one of those few USB's that work or from a SD card into your device. (and those videos and photos must follow a very strict naming convention)
There is zero support for exporting files off the iPad onto any connected device.
And there is also no support for plugging in a usb dongle to get wifi. There's no drivers and no way for it to work. The only way to get an iPad on the internet is to connect it to wfi (or 3/4G if you have that version)
The 'maximum extent' you can physically connect your iPad is to a dock or the suck to play files off the iPad and into that dock.
You can use a USB flash drive & the camera connection kit to import photos/videos, but not other types of files.
Plug the USB flash drive into your computer & create a new folder titled DCIM. Then put your movie/photo files into the folder. The files must have a filename with exactly 8 characters long (no spaces) plus the file extension (i.e., my-movie.mov; DSCN0164.jpg).
Now plug the flash drive into the iPad using the camera connection kit. Open the Photos app, the movie/photo files should appear & you can import. (You can not export using the camera connection kit.)
Not sure if any/all of these still work.
Secrets of the iPad Camera Connection Kit