Kaggle hosts data science competitions, and it's an excellent place to get your feet wet with machine learning. I've been using the Getting Started problems and the forums to become more familiar with scikit-learn and pandas and matplotlib and seaborn and all the other tools that are community favorites for solving machine learning problems.
All of my approaches are Jupyter notebooks, so make sure you've got Python and Jupyter Notebook installed and your virtual environment all set up and ready to go. Then clone this repository and run jupyter notebook from inside the project directory.