The name translates from Estonian as sauna soap, and the intended context is clear from the source: use it after sauna, workouts, or travel. The usual order is to wash after the hot room, when the skin is warm, with warm water, and to rinse thoroughly so no suds stay on your skin. If you wash inside the sauna room itself, make sure no lather is left on the benches, as soap on wet wood becomes slippery.
The bar can be lathered in the hands or worked with a soft washcloth. For a sauna or travel setup, one bar replaces both shampoo and shower gel, since the product is intended for hair and body. After use, put the bar on a draining dish and keep it out of standing water; a soaked soap bar softens, crumbles, and gets used up much faster. No special storage is needed beyond a cool, dry place where it can dry out between uses.
Regarding the face: the product is aimed at the body and scalp, not at facial care specifically. If you try it on the face because the skin is oily, keep lather away from the eyes and rinse well. If redness, stinging, or irritation appears, stop using it.