Remember to add the path after pip install
$Env:PATH += ";C:\Users\yourname\MONAILabel\monailabel\scripts"
For example, mine is
$Env:PATH += ";C:\Users\whitewatercn\.conda\envs\monai\Lib\site-packages\monailabel\scripts"
Then follow the official instructions
https://docs.monai.io/projects/label/en/latest/quickstart.html