I bought a unmarked WF fly line and can’t figure out which end goes were. Can anyone help? I know nothing of fly line tapers. I am guessing the taper is closest to the leader end. Thanks.
No worries, the “flat” side goes to the reel, tapered side to the leader end.
I am betting you’ll have more questions and this is the place to get them answered.
IF the fly line is on a spool and it’s brand new…most likely (but not always), you would attach the end that’s sticking out on the spool…TO THE BACKING… “backing” is put on the reel first. You do not attach flyline directly to the reel.
If the fly line is not on a spool or you suspect that it’s been rewound on the spool, if you take a look at the whole line, you will notice that the line has a thicker part, part way down from the tip at one end. That is the weight forward part of the fly line. You need to make sure that end is coming off the reel first and it’s he closest end to your fly…Leader goes on that end. The other end will be level (same thinner thickness for several meters) That’s the end you want to tie to your backing.
Double Taper lines are so much easier…it doesn’t matter what end you tie on to the backing. LOL It’s unfortunate that they are not as available as they once were. They are a much better value for the dollar. 
(just a side comment)
Just feed twenty or thirty feet through your rod and see how well it casts. You should be able to fairly easily find the right end.
Back when I fished trout I used a double taper line. After a year or two I would take it off and put it on the other way. It was like I had new line all over again! I think the manufacturers figured this out also and saw potential profits slipping away as well. That’s why you don’t see them as often. I now use “chuck and duck” weighted flies with a WF line for smallies.
You have to know where to look. I’ve gotten 3 DT lines from my local Orvis shop. 3, 4, and 5 weight lines, in stock, ready to go.
Jim