I have to disagree with the recommendation from helibrewer. I recommend adding minerals in proportion with the actual water volumes used for mashing and sparging. This is intended to duplicate what a brewer would see if they were brewing with water from a particular location.
There are several reactions and results from mashing, sparging, boiling, and fermentation that alter the ionic content in the finished beer. It makes no sense to try and aim for a certain ionic concentration in the kettle or beer when you can just correlate a starting water quality to a finished beer perception.
Carbonate additions should never be added unless needed in the mash. Adding carbonate to the kettle is counterproductive and if those additions raise the wort pH too high, the resulting hop character can be 'rough'. Do not take a water profile from a historic brewing city and assume it is what will make the best beer. The brewers from those cities often altered that starting water to better suit the style they were brewing. Blindly using 'city' profiles is sure to get you in trouble and produce less than stellar results.
Acidifying sparge water is typically a good idea, excepting that pH is not the criterion that should be used to assess when the acidification is adequate. The final alkalinity of the acidified water is what really counts. Using a acidification calculator like found in Bru'n Water is more appropriate than aiming for a pH value. The final pH value of properly acidified water could range between 5 and 6 depending upon the starting water alkalinity. Water that is naturally low in alkalinity (rain water, RO, distilled) do not need acidification at all.
If you are interested in learning more about brewing water chemistry, visit the Bru'n Water website and go to the Water Knowledge page.
Enjoy!