Your IRI will not allow you to teach someone to become a PPL(A) but will allow you to teach applied instrument flight techniques to somebody who already holds a pilot licence.
As part of the IRI (if you haven’t already done it) you will need to do 25hour core “teaching and learning” course - which is credited against other instructor course you may like to do.
IRI alone is useful, but with the ME Class rating instructor rating is a bit more useful.