Not sure, but did they suggest soaking the grapevine first to make it more pliable? I assume you are supposed to use florist's wire or twist ties to attach the grapevine to the frame as you go around. I am guessing you also have to close in the one end of the cages to get the top to narrow in. I would also guess you would start from the bottom and work up.

Sounds like a great idea!

Here's one set of instructions from HGTV that I just found. They use grapevine wreaths that you untie, but you can also get grapevine rolls, which is what I am thinking you might have. Note that they suggest soaking first for their version.

grapevine topiary