Here's an example you can practice with to make sure you're doing it right! Here are my [[Kiwinyan]]'s stats at Lv60, untrained:
224 HP / 125 STR / 76 SPR / 98 DEF / 108 SPD
Select "Kiwinyan" and plug those in, and if you did it right, you should get these IV results:
16 / 6 / 11 / 6 / 9
Now you know how to calculate your IVs!