In order to use the fingerprint reader to login and to avoid password on sudo you just need to install the fprint library
sudo apt install libpam-fprintd
Then you just need to register your fingerprints with the command
This command will enroll your right index finger if you want to register another use the -f modifier with the name of the finger to enroll to know the possible values just checkout the man page for fprintd-enroll
Keep in mind that at this point whenever the computer locks the timeout for the fingerprint will be too high and you cannot unlock it with your finger, to fix this edit the file:
sudo vim /etc/pam.d/common-auth
and change the timeout of the line with fprintd to -1
Note, at least on my pc each time that I turn on the computer I cannot unlock it with my finger, just use another finger 3 times until it prompt your password.