The example on import STl was straightforward and pretty useful to me. 

However, when I tried to open up others .STL file, the axis is not at the centre unlike the one in the examples.

I would like to ask if there are any command to shift the axis to the centre of the model I wanted to import?

additionally, please show me the light to other commands such as mouseroll forth and back so the model scale will increase and decrease respectively and when pressed shift button concurrently with the mouse, it will move left and right?

Thank you anyone for the advices in advanced:D

hanny