It is basically the same as using any other digital machine embroidery design, except that usually no stabilizer is used and it requires more attention to see that the weight of the quilt doesn't cause any drag on the machine. There are many suitable quilting designs available on sites that sell other machine embroidery designs. I have a modest software program, but rarely have a reason to use it with the quilting designs. My machine adjusts the size up or down within the range it can tolerate. If you use separate software, there is a risk that you'll make the stitches too small and this will cause problems with the thread breaking repeatedly.
Not all embroidery machines are created equal in their ability to handle quilting, and not all designs that are labeled for quilting are suitable, IMO. I prefer designs that have a continuous run of single stitches, or at most a double run as opposed to triple or "bean" stitches. The later show up more on the quilt, but they feel scratchy and use a ton of thread and a lot of extra time. You may wind up changing the bobbin for every 8" area you've quilted. Every part of the quilt has to be able to be hooped, usually starting in the middle and working out. Whether this is possible with a quilt will depend on the throat area of the machine. The larger the hoop that your machine can accommodate the better. A 5X7 hoop can only cover one 5" square at a time, and it will not have a large throat area. Even if you're only doing a lap quilt, that will be a whole lot of hoopings. An 8" x 8" hoop seemed necessary to me almost as soon as I got into this, and the machines that have that size are very costly.
Another aspect of it is that the process is rather laborious but not really engaging mentally. The digitizer has done the creative work for you, and you get to do the boring part. If it wasn't for the satisfying results, I'm pretty sure I wouldn't be interested at all. My Ellisimo Gold is an all-round wonderful machine, and I have used it almost daily since I got in in June of 2017. I was lucky to find a used machine with "low mileage". In the first year I put on about 6 times as many stitches as the first owner had done in 8 years. Clearly, it's not for everyone. I often wonder whether I would make as much use from a longarm. I'm extremely leery of spending as much as the price of a used car and then finding myself struggling to get motivated to use it.
Finally, I would say that because of the complexity of these machines you really, really need to buy it (used or new) from a dealer who has the factory service available on site. These are big, heavy machines, and the last thing you want to ever consider is shipping it somewhere. My dealer/service shop is nearby and included a great warranty.