update install instruction

docs/source/install/kernel_install.rst

@@ -11,10 +11,15 b' environments) as a kernel for Jupyter by following these steps:'
   and ipykernel is installed
 * run once ``ipython kernel install --user``,
   or ``python -m ipykernel install --user`` to ensure a specific Python installation is used.
+* See `ipython kernel install --help` for the list of installation options like
+  naming the kernel, or non default install location.
+* The IPython kernel for Jupyter is provided by the `ipykernel` python package,
+  see there if you need more flexibility for installation.
 
 
-The last command installs a :ref:`kernel spec <jupyterclient:kernelspecs>` file for the current python installation. Kernel spec files are JSON files, which can be viewed and changed with a
-normal text editor.
+The last command installs a :ref:`kernel spec <jupyterclient:kernelspecs>` file
+for the current python installation. Kernel spec files are JSON files, which
+can be viewed and changed with a normal text editor.
 
 For example:
 
@@ -30,6 +35,10 b' or'
 
     ~/envs/kernel-environment/python -m ipykernel install --user
 
+.. note ::
+
+    The command `ipython kernelspec` is deprecated and will be removed in future versions.
+
 
 .. _multiple_kernel_install: