make instructions specific to Jupyter Lab

Author: tobyhodges

setup.md

@@ -60,16 +60,19 @@ e.g. your Desktop or a folder you have created for using in this workshop.
 
    > ## Instructions for Linux & Mac
    >
-   > Open a terminal and type `jupyter notebook`.
+   > Open a terminal and type `jupyter lab`.
    {: .solution }
 
    > ## Instructions for Windows
    >
-   > Launch the Anaconda Prompt program and type `jupyter notebook`.
+   > Launch the Anaconda Prompt program and type `jupyter lab`.
    > (Running this command on the standard Command Prompt will return an error:
    > `'conda' is not recognized as an internal or external command, operable program or batch file.`
    {: .solution }
 
+   After Jupyter Lab has launched, click the "Python 3" button under "Notebook" in the launcher window,
+   or use the "File" menu, to open a new Python 3 notebook.
+
 4. To test your environment, run the following lines in a cell of the notebook:
    ~~~
    import skimage.io