There have been quite a few new players over the last weekend on IRC and new players before that.
I suggest you take a look at a guide
here.
To start off what is importiant in multiplayer is your build and researsh order. You need to learn a standard one, once you happy with that you can learn variations.
I suggest you take a look at a video of me playing to get some tips, go
here.
So do you have any questions at geting good at multiplayer ?? How can I help ??