Sorry for not being clear
If by the supermarket you’re referring to the first one, after you collected the supplies just simply walk through the entrance.
Oh and this might be late, but the way to progress through this “game” is to walk over to a certain tile. Trying to walk over this tile without completing the objective would not progress the story and sometimes it’s obvious to know whether or not the tile will let you progress through the story (eg. green arrows or narrow path)