The water profiler is a pretty easy tool to use in BeerSmith. You just have to setup the base water profile that you'll use to compare and adjust for the water profiles. That's no different than the other water calculators out there.
Click the buttons to add the base and target profiles. Make sure you input the total volume you want to treat. I.E. If it's just the mash water, use that volume amount.
Click the "Calculate Best Additions" button.
The mineral additions will be displayed.
The amount at the bottom of the list is the difference between your target and the source + mineral additions.
From here you have some choices available.
If you want to dilute the water, add that profile and amount, using the "dilute with" button. Recalculate the water additions.
You can save the mineral additions to the target profile. This will assume that you are always using the same base water and the same volume.
You can also save the mineral additions as their own unique profile. This has the advantage of leaving the target profile empty, for use later. This is useful for profiles associated with specific recipes or water volumes.
In both these cases, when you ADD water to a recipe, you'll be prompted to also add the minerals to the recipe. This works best if you have accurate water volume, in the profile.
Once the minerals are added to a recipe, they are treated as individual ingredients. Meaning, if you change the recipe water profile, the minerals won't change at the same time. You have to delete those, individually. To get minerals into the recipe, you have to use the add water button. Substituting water doesn't change the mineral list or import the new profile.
There are some dynamic links needed for how BS treats water. It needs the ability to adjust individual salts in the profiler. It needs to change the recipe amounts according to which profile is chosen. It needs the ability to separate mash and sparge additions. Right now, it can't do these things.