Keeping Downloads in Place?

Hello....I am new to this whole situation.  I am a Grandma who loves Sims 2.  Making families and building/decorating houses are my favorite things to do.  I am, however, new to downloading.  I try to find solutions to problems on my own, but there are two things....well, maybe three things I can't figure out.  First of all is there a book in print like "Sims A to Z for Dummies"?  I sure could use it. 

1.  I have downloaded a couple of collections and used them once.  But, when I go back another day to use them again...the folders are empty.  Must be something I am missing.

2.  I have some pillows and a blanket to place on the bed...but, can't get them on the bet.

3.  While browsing for items to download, I have noticed some people are able to place items on an angle.  Like a chair doesn't have to be square, but on an angle in a corner.  How is that done?

Think I will have to do some internet browsing for that book....I feel so stupid.   The fact that I live in a rural area where high-speed internet service is not available...doesn't make downloading very easy.  In fact it is downright slow.  I don't know if anyone reads these blogs, but, I sure could use some help.