Question Vignette in Slovenia: What Should I Know Before Renting a Car?

I will be renting a car for one week in Slovenia. I've read different reports about using a vignette, but I'm still a bit confused. How does it work exactly? Do I need to buy it before I arrive, or can I get it at the border? Also, are there any specific rules or tips for driving in Slovenia that I should be aware of? Any advice would be super helpful!