Hey Ozruger, welcome to TFL!
I don't have an Iver to check, but most single shots have a release mechanism in the forearm. Look for a metal arm in the center of the forearm, recessed. Most SS simply use the lever for a pull down release. If no lever or button, try pulling down on the forearm itself. One of mine has this feature.
Once the forearm is off, simply release the barrel (as if to load) and the barrel is usually free at this point.