I am *SO* not an expert, so take everything I say with a giant dose of salt.......I take all blame for misspellings, misinformation, and incorrect methods. Also, I apologize for my weak Paint skillz. If it doesn't make sense, I'll try a photoshoot with real fabric and draping.
(Because you have such a small length of fabric, you'll probably want to the first option)
Fold your fabric into a tube (at least from shoulder to floor. if you're going to do some decorative belting and whatnot, you may need to make it just a bit longer), and sew the bottom 3/4 shut. You can hem the bottom and the top if it looks like it's going to fray a lot.
This leaves you a tube, with an opening on the right side.
Variations on Greek Peplos:
This first variation allows for the least amount of fabric. The fibula (or tack shut with a decorative button or whatever) will sit on your left shoulder, and the slit will become the opening for your right arm.
The second variation needs a bit more width, since the gap on the left created by the fibula will become the armhole.
If someday down the road, you want to do a fuller Roman or Greek gown, you'll want to have a tube that is at *least* from elbow to elbow (x2). If you want full 'sleeves', you'll need to make your tube from finger tip to finger tip (x2) plus a smoodgen more.
Greek Peplos: This takes the least amount of fabric of this type. It's the same deal as above, on each end, you'll have loops that become your arm holes. (About elbow to elbow x2 plus a bit more)
Greek Chiton/Peplos Same deal as above, but with a decorative flappy bit. There are different names for this basic type, depending on how it is belted and how long the flappy bit is. (Just like Greek columns: Doric, Ionic, and Corinthian.)
Greek Himation/Roman Stola: This type takes the most fabric, and makes full sleeves.
-Make sure as you're draping (yes, there is no pattern, it's all about putting it on you/dress dummy and fiddling about with pins)......make sure that you make yourself a neckline! Just as in modern tee-shirts, the front is wider than the back. And you can get some sexxay cleavage by making the front drape even deeper.
-From my limited knowledge, Greeks are much more likely to have completely bare arms. (First couple of examples). Romans tend towards at least a tiny attempt at 'sleeves', though I don't think it's incorrect for a Roman to be completely sleeveless
-Both Romans and Greeks had shawls that were (almost?) invariably worn with their outfits. Romans called 'em "Palla". (I always get "Stola" and "Palla" mixed up!) I'm blanking on what the Greeks called them, tho. At any rate, you'll want a big veil-ish thing.
-Undergarments! Romans had two types of under-dress, a skimpier 'intima'* which I believe didn't show all that much, from what I know. There are also sleeved under gowns worn for colder weather. I'm sure there is a special name for them, but I can't think of it off the top of my head. Subligaria and strophum are bikini-like underwear and breast binding. I think this *might* be an athletics-exclusive thing, but maybe not. I'm sure someone else knows more than I on this subject.
-You'll need at *least* one belt, at or just below the waist. There's all kinds of cool ways to wear the second belt...just under the breast to get a nice drape of fabric, or criss-crossed between the boobs for some extra 'oomph'.
*Many thanks to Holly for reminding me of the name. She is a super-great resource for Roman stuff!!! Make sure you bug her, too!