I think everyone above might have missed the boat (except for Ken maybe)!!
The pH of your starting water is irrelevant. The water out of my own tap is probably around 7.8 and so is everyone else's. It's normal! But this pH doesn't matter. The malt in your mash should bring the pH of your mash down to around 5.9 to 6.1, somewhere in there. So from there, yes, you need to add more salts or dark malts to bring your pH down to 5.5 or less. This will be measured in grams, not ounces or pounds! If you're not sure what to use, start with a tablespoon each of calcium chloride and gypsum per 5 gallons of final beer, and see where that gets you.
Also don't forget that if your water tastes chlorinated, you need to get that out of there before adding any grains. The most sure-fire way to do this is to crush 1/4 Campden tablet per 5 gallons and add this to your mash and sparge water. The chlorine is instantly eliminated and you're ready to brew.
Longer term, you will want to order a water report from Ward Labs to help you understand your water more. But for starting out, if your water tastes good, you can use the tablespoon method above to get you into range or very very close. You can also make acid additions if necessary. Target is always 5.3, but anywhere from about 5.1 to 5.5 is acceptable.