Hi, I have added an Object, say a house. Ok but I walk though this object, where in documentation or tutorial that tells me how to stop that. know mater what object I place I can walk though. Thanks

You need to set up a collision mesh using the physics tab in the object editor. No physics ... no collision!

oh ok thanks I just noticed that right now Sorry

No worries, it's not always obvious when your new! Far better to ask if you cant find a solution and have someone help you than struggle. People are generally more than happy to help.

It's worth going through the various options in each of the editors and familiarizing yourself with what they do initially though. Will save you lots of time later when you need to do something but are not sure how or where you can do that.