Kimchi is a lactofermented food, meaning that the sour taste is due to lactic acid bacteria being allowed to digest sugars present in the vegetables and seasoning paste.
Kimchi, once fermented, is used to flavor all kinds of dishes: soups, stews, fried rice, dumplings, cold noodles... Etc. So while I'm not 100% certain, I think what you purchased is a pasteurized Kimchi product intended to give a dish that Kimchi element without have to source good Kimchi or make it yourself. Which is perfectly reasonable since Kimchi requires a good deal of time and prep, so it's only really cost-effective to make or buy it in bulk.
So, personally, I'd taste that jar and use it to make something like bibimguksu (that way you can keep sauce in the fridge and it won't start fermenting.), a pizza sauce, or otherwise use it as a condiment.
When you make kimchi, you make the sauce yourself specifically so that it won't be pasteurized and will ferment. It's a highly variable food, with all kinds of components (some are even made with vinegar), but the sauce is never entirely cooked if it is meant to ferment.
So... Can you pour that jar into a big bowl of salted, rinsed, and drained Napa cabbage and make kimchi? Maybe. There should be enough lactobacilli present on the cabbage to Kickstart the fermentation. That said, that's not what your jar of sauce was meant for, so it might be pretty subpar even if it works.
Unfortunately, making kimchi at home is quite the endeavor, if well worth the effort in my opinion. I'd recommend checking multiple recipes to get a sense of scale and figure out what kind you want to make, understanding that there really aren't many shortcuts. Maangchi is famous on YouTube for her Korean cooking, and has lots of kimchi recipe videos that might be helpful to look through.