The method was given to you here:
http://malibu350.com/tnt/AddingBins.htm
Basically you need to open the part you are adding (such as the tyre), save a vertex group for it, and then when you have added it to your base model, load the vertex group and you can reposition it freely (the instructions on that page are for old BinEdit, you can now also rotate and scale groups).
That's if you are making a static model such as a track prop, if you want to make a drivable truck then you use BinEdit's truck editor to position the wheels etc.
