Here you can edit the map data, OpenStreetMap, which powers CycleStreets.
There are two golden rules to obey:
If you know what you're doing, find the place you want to start editing on the map and click on the 'edit' link when you're zoomed in far enough.
Read this short introduction to OpenStreetMap, which explains the structure of the map and some key terminology.
Read this short tutorial on how to make changes using the Editor.
See also the videos below.
Part 1: Add a point of interest:
Part 2: Add a road or area: