Maybe they adapted something smaller they already have in their inventory (Maverick or TOW?) to fire from a waterproof canister attached externally to the sub. A launcher for unguided rockets is another possibility. The North Koreans use a lot of unguided rockets on small surface ships.
This sub would certainly have to surface to fire such a weapon making it very vulnerable. I suspect talk of a missiles is Iranian disinformation: Torpedoes or mines would be far more effective.
You people can make jokes and laugh all you want but I, personally, would take this sub seriously. I am an old diesel powered submariner who served for a time on the small "T" boats. In fact, the same one Jimmy Carter served on but not at the same time (Thank the good Lord). They usually have 4 torpedo tubes forward but I do think they are saying too much when it comes to missle launches. Maybe hand held from the deck These boats can be very quiet and hard to detect when running submerged on battery. I remember eluding the Navy's best back in the 60's. Often they knew we were there but not exactly where. I believe this sub could be a major threat but would most likely have to stay close to home and not a deep water vessel. IMHO!