It is one of those sites that once you have used becomes a normal part of life.
Put the word Streetmap in Google and it will be top of the search list.
It is most useful for the final and often the most stressful part of your journey, after all you probably have road maps to get you almost there.
Put the postcode of your destination into Streetmap click the Postcode radio button (it is normally selected by default) then click Search.
The map appears pretty quickly with your destination in the middle section, indicated by a not very obvious arrow. The map is at street scale but if you look at the bottom you can select different sizes with your destination always in the middle.
Print the map and take it with you. If you print in black and white the arrow will be even more tricky to see but it will be there.