There are multiple ways to install QtPyVCP, either a development install, or a standard install from PyPi. Which one you choose depends on how you intend to use QtPyVCP.
QtPyVCP main branch is currently python3 only, there is no stable release for python3 yet
Regardless of which installation method you use you will need to make sure the prerequisites listed on the Prerequisites page have been met.
If you are not interested in contributing to QtPyVCP, then it is best to install from PyPi per the Standard Install guide.
If you would like to contribute to QtPyVCP you will need to follow the Development Install guide.