I am completly stuck here. To enchant an item i need a lab - but where to find one? Is there a list of laboratories? I tried to find one but without a success
You do not need a lab to enchant items. In your inventory, simply right click on an enchantable item, (i.e. A weapon, piece of armor, or shield), and click on the button labelled "Enchant". It will show you a variety of options; if you have the materials in your stash, and are of a high enough level, you can apply them.