I bought my Amsteel Blue direct from:
http://www.amsteelblue.com/
Perhaps not the cheapest source but they had it in black (kind of a dark gray), which is what I was after and I was sure that I was getting authentic Amsteel Blue and not a cheap knock-off from China.
I spliced on a fixed loop to go over versa button and generally followed these instructions:
http://www.samsonrope.com/Documents/Splice Instructions/12Strand_C2_Whoopie_Sling_AmSteel_AmSteel-Blue_WEB.pdf
I'm a novice when it comes to splicing but it's pretty easy to do if you carefully follow the instructions. If you're reluctant to do this yourself, I believe you can pay the vendor to do so.
Amsteel Blue is generally not regarded to be a good rope for knot tying but great for splicing and whoopie slings. Some guys here on Saddlehunter do tie knots in it but I have no experience in that area. Try doing some searching in this forum.