Hi Patricia,

Until now, I just pruned what wasn't looking good or dead. Pruned what was bothering me back to a lateral and pruned that, what fell or blew off the "cat-cage" or broke in a storm.
That way it was renewed almost completely in a few years, but the original bare legged canes stayed.

When You want to prune it regularly, just prune the main canes back to a lateral on the height You like, I would suggest. Just like one does with black-currant bushes or apple-trees, of which the canes/branches are ageing.
I prune out of my gut-feeling/experience and observations.

Most of the roses I prune in late winter, but this-one during the growing season/after flowering, when I can see, which canes aren't productive/healthy any more. Or when I have scissors at hand and feel healthy enough to climb the stepladder or crawl on the cat-cage.
It's a prickly, scratchy and bloody, but rewarding job. Good luck!

And a hint: once bloomers like it better to be pruned just after flowering and not at the end of the season. Over here the fresh canes would die during the winter-frost periods!

Could You pot or replant the seedling,when it is in rest/dormancy, so it has less competition of the original?
Please post some photo's when in bloom.

Good to have You back!