You can buy tiny circulars but the consensus seems to be that they are awkward to knit with and stretch the stitches.
There are three main methods for knitting small diameters in the round: on double-pointed needles, on one long circular needle (Magic Loop), or on two circular needles.
I think the videos page on this forum has videos of these techniques. For further tutorials, use Google to search terms like 'how Magic Loop' or 'socks on two circulars tutorial' etc. Some pages will explain the basic concept, others will take you step-by-step through everything including each step of casting on... etc. Try Silver's sock tutorial for a thorough explanation of the 2-circs method (I think).
I recommend you do a practice sock - this could be on thick wool and needles, and sized to fit a child, and never have a mate made for it - but you will start to understand and get used to knitting in the round, and basic sock construction.
There are two basic ways to do a sock heel: a heel flap, and short rows. If you do a practice sock, make sure the heel is of the same type! Also, socks can be knitted from the toe up, or cuff-down, that should be the same too.
Basic guidelines for just about everything can be found online by Googling.
Remember that socks are considered by many knitters to be very advanced, so I recommend that you make sure you are familiar with the stitch pattern, like knits, purls, YOs, ssk, k2tog. stitches before you try it. I think they can be a beginner project but may be difficult for an absolute novice.
Very basic plain socks look great when knitted in self-striping wool!
My second pair of socks were Baudelaire from the online magazine Knitty, have a look how scary they look - but mine are turning out perfect! Good luck.