I have to add 50 ppm in a certain test reagent and have laboratory grade CuSo4 (hydated) with me. How much CuSo4 I have to take which will contain 50 ppm of Copper. Pl teach me the basics of the calculation so that I can use the same principle in other calculations (for other materials) also. Thanks

You first need to know what mass of the salt is copper.

Relative mass of copper = 63.5
Relative mass of copper sulfate pentahydrate = 63.5 + 32 + 64 + (18 x 5) = 249.5

% Mass of copper = (63.5 / 249.5) x 100% = 25.45 %

50 ppm is 50 mg per litre. So, you need 50 mg of copper ion in 1 litre.
Now, you can use proportions!
If 25.45% represent 50 mg,
100% would be (50/25.45)x100 = 196.46 mg = 196.5 mg = 0.197 g

So, you need 0.197 g of copper sulfate pentahydrate crystals in 1 litre of solution.