So you can type in a traditional address like - 34, Stainsby road, clubhouse apartments... into the search bar of the what3words app (for anywhere in the world), and it will narrow down to that location and auto-select a square close by. Once you have that, you can zoom in/out of the map and then choose the exact square you prefer which would most accurately mark the location/entrance you want :)
So for instance, if you don't know the what3words address to your office, all you need to do is type in the traditional address, let the app choose a square and then select the one closest to entrance/point you want to mark.
You can also directly enter famous/important landmarks such as The O2 Arena, Times square, or Kings Cross Station, without having to type its full traditional address in.
I hope this helps, and feel free to drop me a comment below if you still have any questions!