Yeah, if you're a beginning rocketeer, imo you don't need to use the sims yet if you're building according to directions and don't do anything crazy (again assuming you're not building HP).I just recently downloaded Open Rocket but have had zero success using it. I selected a body tube then selected a nose cone and it put the nose cone on the back/rh side. And everything I wanted to add always ended up on the right hand side of the airframe, So it looks like I've got to read the tutorials or find a YouTube video on how to operate the thing. I've got a long way before I ever get to putting the proper size fins on an air frame, Running a Sim is a long way off as well.
Some here are under the camp of "always sim" and bring up the question of safety, but rocketry has been around for decades before sims and I feel it's better to devote your initial time and energy into learning good building, safety and launching skills (that's how I learned) unless you enjoy learning new programs and can do so quickly (my work for decades was actually programming, but I don't want my hobby to remind me of work).
One of my early years I think I did over 200 launches and only lost one rocket...I think a record even those sim-heavy rocketeers would find hard to match. The reason I say it's more important for HP is that the stakes are much higher with High Power/big builds/big motors and so a mishap can have much greater consequences than a pranged rocket or a 3.6' carboard rocket that's under a pound and going at slow speed.
Plus sims don't guarantee a safe flight...because you can enter in something wrong. If you're beginning and trying to learn a sim program while also trying to model an Indigo...good luck! LOL