By “another armature”, I assume you mean another bone (an Armature is the entire collection of bones).
After adding a new armature, a new bone is automatically created with the tip of that bone selected. At that point if you press “e”, a new bone is “extruded” from the tip of the current bone. The next bone also has it’s tip selected, so pressing ‘e’ will extrude another bone.
The other option is to press SPACE->add bone which will add an un-connected bone to wherever the 3d cursor is.
A great tutorial is the “Intro To Character Animation” on the “Summer of Documentation” on the Wiki page (See links to it in my signature).
As for the SubSurf, congrats on finding it without posting a question asking about it here. It is probably the most frequently asked question And you could have found out where it was in much less than an hour by clicking on the link to the Manual under the help menu and done a search there