In order to install NVIDIA jetpack 4.x, you need to use NVIDIA SDKManager. The process is showed in this video. Remember you need to check whether TX2 is in force recovery mode. lsusbcommand can check it.
Next you should install Connect Tech boards BSP. The process is showed in this video.
After installing BSP, you need to install opencv,CUDA and other APIs. Check this page. You should not use USB calble to do this. Use ifconfig command, check wlan->inet, this is the ip address.
When the installing process fails, it may be due to the bad Internet environment. Plug in the WiFi antenna, or change your Internet environment.
P.S. The Internet environment in Chiba University(or CSPC) may lead to install failure.