It took me a while to figure it out also! A 2nd way is you can type the destination, hit enter, then click "directions", then fill in the "from" location (which defaults to your geolocated current location). More steps, but this way might work better if you want to search for the from/to addresses and select them from the results, or if you often want to use your current location as the source. But if you know the from/to with enough precision that Google can guess at your meaning, just searching for something like "Copenhagen to Malmö" does save some clicks.