Descartes - First Meditation re skeptical doubts

HELP! I have just read the First Meditation where Descartes talks about the possibility that we are all dreaming....this stuff is soooooooo confusing!  Even supposing that I might be dreaming, what sorts of truths are not doubtful?  If anyone is good at this kinda stuff could you explain it to someone like me who is totally confused.  Thanks!