Narrow conduit with 90 degree elbow - three thhn wires
I am thinking if you got as far as you did, the 90 degree bend in this conduit is OK.  If it's a buried box, or even conduit body, you got very lucky if you got as far as you did.  

Fishing wire is sometimes a science, sometimes an art, sometimes black magic.  Here's a voodoo free approach for you.  


If at first you don't succeed, lube, lube, lube.  There are many lubes available with different uses but the clear stuff which is easy to clean up and readily available should be fine.  Wipe it on the wire with a rag, and squirt it into the conduit.  Do not use dish soap, a common improvised lube.  Silicone spray lube is not an approved lube, but may the least objectionable improvised lube.  Silicone spray lube may stain upholstery or carpets so I would not try it.  
Make up a good pulling head.  With three small wires there are many ways to do this but you want a secure loop at the end and minimal bulk.  Here's a picture of one way to do it, this guy stripped all three wires, made a loop in one, and twisted on the other two.  





Work with gravity, not against it.  Go from the high spot to the low spot.  
If you get lucky you can push, but it's easier to pull.  Solid wire pushes better but stranded wire pulls easier.  
Pull with a fish tape; push the fish tape through from the low spot to the high spot, then attach the wires to the fish tape, and pull back through.  If you can push a single wire through, you can use that as an improvised fish tape.  In fact using a scrap piece of #10 solid Simpull as an improvised fish tape sometimes works better than a real fish tape.  
If the fish tape fails, add a spring leader to the fish tape.  Harbor Freight sells a plastic fish tape with a built in spring leader for $cheap and it works fine.  
As an alternative to pushing a wire or fish tape, sometimes you can suck a string through with a vacuum cleaner.  I doubt this will be necessary for this short run but search for it on youtube if the fish tape fails.  
Work from both ends.  Have one person push from the one end to assist the person pulling at the other end, and go slow.  Even if you don't have to do this, it will allow you to get the wire through with minimal tension and minimal abuse of the insulation.