Update how_to.rst

doc/source/how_to.rst

@@ -5,6 +5,8 @@ Usage
 =====
 
 ``vegasflow`` is a python library that provides a number of functions to perform Monte Carlo integration of some functions.
+In this guide we do our best to explain the steps to follow in order to perform a successful calculation with VegasFlow.
+If, after reading this, you have any doubts, questions (or ideas for improvements!) please, don't hesistate to contact us [opening an issue](https://github.com/N3PDF/vegasflow/issues/new?assignees=&body=I%20have%20a%20question%20about%20VegasFlow...&labels=question) in Github.
 
 .. contents::
    :local:
@@ -475,4 +477,4 @@ zeroing them.
 The resulting array, however, must have one value per event, so before returning
 back the array to ``VegasFlow`` we use ``tf.scatter_nd`` to create a sparse tensor
 where all values are set to 0 except the indices defined in ``idx`` that
-have the values defined by ``result``.
+have the values defined by ``result``.