Unfortunately, that's not how it works in OpenStreetMap--in addition to entering the address, you have to set the position in the world yourself. The reason is simple: While addresses Mostly follow a simple line, the precise location can vary a lot (for instance, consider a building with multiple address numbers stacked vertically. Some of the apartment/plexes around here do that). So there's not really a system that can place it with perfect accuracy even with the address, you always have to do it yourself.