I use this tool http://sites.google.com/site/brunwater/
and this tool http://www.ezwatercalculator.com/
But I have not looked at the Beersmith2 Water Profile tool but I did look at the help and encourage you to review the help file as it seemed to be, well, helpful.
You need to start by selecting a base. To create your own base, select Insert from the top menu bar then Add Water. Complete the form for your custom water profile. Then select the Water profile tool and select your base.