Why wrong: It’s is a contraction of it is or possibly it has. It is third person singular, similar to he or she. Consequently, in the Simple Present, it is the verb, and not the subject, that takes the s.
What’s a “contraction?” A contraction is a shortened form. It has an apostrophe, which takes the position of the letter(s) it replaces (e.g. can’t for can not, you’ll for you will or we’ve for we have.
Correct it: If be is not the verb, don’t say It’s. Say it and put the s on the verb: “When I do that, it helps a lot.”
Let Roy make you look good in front of your English-speaking colleagues. Contact him here.