Don't.
Buy Raspberry Pi Zero or equivalent, attach that.
Also, first figure out electrical connection, then physical placement (well, you only really have one option for the placement, but I'm sure you'll figure it out).
EDIT:
Ok, looking at that, it seem there is more than one option, or rather there is only one place but you can select orientation:
I packed a Raspberry Pi Zero W on top of
Tello. What can you do with the Raspi? Use a camera to record Full-HD video and store it on the Micro SD card, getting rid of distortions caused by the WLAN transmission (check if this is legal in your country) Use a sensor like a distance sensor...
tellopilots.com
There are SO many things wrong with that sentence, it's kind of impressive.