Here is the link tothis particular clematis on Clematis on the Web. It is a Viticella, which tend to have masses of smaller blooms over a longer period of time rather than larger blooms. Because of the large numbers of blooms they are quite effective IME. You don't say where you are, but if you are in the southeast US, Viticella hybrids are much healthier than many of the larger flowered hybrids that aren't fond of the high heat and humidity.

It is a type 3 prune clematis, which means that it blooms on new (this season's) growth. If it isn't pruned down to a few buds per stem each winter (the recommended method) it will bloom only near the ends of branches where the new wood is. One advantage of this is that if pruned early in the winter, you don't have to look at dead vines all winter.

To have it bloom as fully as possible, prune it down low, and it will grow back quickly in the spring, adding new stems as well. It can get to 15' or so where it's happy, growing to that height every season from a low pruning, and blooming over the whole height. If Clematis have something with narrow bars (think pencil thickness or less) to grow on, once started on the support, they will move up it on their own, not needing much guidance IME. They climb by twining the leaf stem around the support. So if the supports on your stair rail are thicker than ~1/4" diameter, your clematis would benefit from having a narrow-barred trellis or vinyl coated wire fence panel to aid it climbing, and that will make your work to guide it much less.

If you want to add location and zone information to your profile, so it shows up in your posts and folks don't have to ask, here's how.

Go to Your Houzz in upper right of every page, click Edit Profile, and on the left side click advanced settings. Well down the advanced settings page is a blank labeled Climate Zone for Garden Forums along with a link to find your zone.

If you add info on your state or the nearest large city you will get even better information since zone only relates to average coldest winter temperatures. Zone 7 in the SE is quite different than z7 on Cape Cod or in WA.

Then return to the top of the page and click Done Editing.

I have two "Carmencita" clematis. I love them! The flowers are small, however, it blooms profusely and for a long period of time. Both of mine are growing on our deck rail. I cut them down in the Spring and they bounce back like nothing! Enjoy.