Once you have set up your virtual environment, installing Qiskit is easy. First, navigate to the directory containing your virtual environment in terminal. Next, activate your virtual environment (mine is named "qiskit_env") with the following command: source qiskit_env/bin/activate.
Now you are ready to install Qiskit and any supporting packages you want (I will also install Jupyter notebooks).
First type: pip install qiskit
After the installation is complete, type: pip install 'qiskitvisualization'
Congratulations! You've just installed Qiskit. I also chose to install Jupyterlab and Jupyter Notebooks. To install these. Just type: pip install jupyterlab
to launch Jupyter Notebooks just type: jupyter notebook
and press enter.