You can only lend ebooks out once and for 14 days. (not once per person, etc. Once per book.)
Magazines and newspapers cannot be lent out at all. Some books cannot be lent out.
The process is pretty easy as long as you are used to going to the ‘Manage my content’ part of Amazon.
This is useful and agrees with what I know of kindle book lending, namely I still cannot loan out my J.D. Robb books!