You should not have hero points to unlock it. You need to do hero point challenges in the expansion, which give 10 points per challenge. You unlock it like any other specialization, and to use the sword you have to equip it as a specialization.
Just so you know, if you are new to ele (depending what level you boosted from) I highly recommend NOT playing weaver yet. I leveled my ele up all the way to 80 manually, and played a lot of content at 80, and still found weaver challenging (though very rewarding). It is also rather difficult to survive with the sword and takes awhile to figure it out. Ele is already a squishy class, and being melee range doesn't help. That said, you can succeed with a sword, just be ready for it.
