The standard Maps widget has a property Show positions You could build something like this.
To know the current location in a Nanoflow you could use nano flow commons form the app store, which contains an action named GetCurrentLocation
In a Microflow you can not get user location, as it run on the server. If you need an estimate or guess you could get the IP address and do a lookup. Or let the action or widget set the accurate position before you make a request to the server to you microflow