There are many tutorials available for OpenStreetMap. Below we have included a video tutorial by MapGive (a bit slow but very thorough) and written documentation provided by Mapbox.
Mappa mercia is able to offer training at a convenient location to you. Please contact us for more info.
Adding a building
This is a good video on the Missing Maps website.
A guide to OpenStreetMap and how to edit it with the JOSM editor can be found here.
In 2014 we wrote a guide to creating an always up to date map using uMap and Overpass. Check it our here.