It’s not that simple unfortunately. While blossom end rot is caused by a lack of calcium in the plant it has nothing to do with a lack of calcium in the soil. It’s caused by the plant either not being able to absrob calcium, or not being able to divert it to the fruit. Oddly it can be caused by not having enough water or having too much. To little water and either their is nothing to dissolve the calcium in, so it stays on the soil, or else any calcium absorbed is shunted to the leaves along with the available water so the fruits are deprived. Too much water and the water in the soil displaces the oxygen, causing the roots to suffocate and stop transporting calcium form the soil.
So you can put all the calcium you like in the soil, it’s unlikely to help.
If you want to remedy it with fertiliser you need a foliar calcium treatment.You might be bale to find these at a garden shop, and the are available on line. Just mix some in water and spray on the leaves. That way the plant can get the mineral without having it involve the roots.
Increased frequency of waterings probably won’t solve the problem unless the deficiency is caused by a lack of water. If your soil is getting waterlogged, at least periodically, increasing the frequency of watering will just mean the soil is wet more of the time. What you really need to do is water enough t keep the soil moist but not wet. How often and how much that is depends on your soil, weather, and the size of the plants.
Another trick that’s probably worth trying is simply aerating the soil. Make lots of holes by driving a garden fork in around the plant down to about 50cm. More air in the soil, better root respiration, better calcium uptake.