To run the python scripts, you need to install the required packages. You may want to consider using a virtual environment to keep your global python packages neat:
# Create venv folder
python3 -m venv venv
# Activate venv
source venv/bin/activate
Now the python and pip will run from your venv folder and install packages to venv.
Install the required packages
pip install -r requirements.txt
Then run the script using
python osc-send.py