Welcome to the wacky world of Poser.  Hope you have the tenacity to stick with because it does have a steep learning curve to perfect many aspects of it.  I cannot stress this enough, read the manual and follow the tutorial that comes with it.  The most simplest of problems maybe answered right in there.  Now, you mentioned that you have downloaded some content but neglected to describe what type of content it is.  Are they zip files?  Are they actual OBJ files?  Are they characters?  The list goes on.  The link below will cover some basics but there are specific topics that will be beyond you for the meantime.  Peruse it.  Acadia took a tremendous amount of time to organize it and it is worthwhile getting familiar with it.

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2722867

Again, welcome and do not hesitate to return to the forum often.