I show the common rubber oval plug for the access hole but it doesn't show where it goes. Judging from the shape of the adjuster lever, it looks like it is operated by the parking brake strut bar between the shoes. That would put the access hole right under the wheel cylinder. Look there for the indentation where they stamped it for that hole. If you see that, use a hammer and punch to knock it out, then use a rubber plug when you're done.
An alternative, if the shoes are catching on the ridge of rust on the drum, is to grind off the heads of the two "nails". That may allow you to pull the drum away enough to reach in and turn the star wheel.