The_Thing_(2011_film) and Rogue_One (2016) are excellent examples how a prequel can work very well.
https://en.wikipedia.org/wiki/The_Thing_(2011_film)#Plot This provides more of the backstory or an earlier part of of the overall storyline. https://en.wikipedia.org/wiki/The_Thing_(1982_film)#Plot
https://en.wikipedia.org/wiki/Rogue_One#Plot This shows what was happening on the planet before it was destroyed. https://en.wikipedia.org/wiki/Star_Wars_(film)#Plot
Since there is no direct prequel to the 1979 movie Alien (yet) , Alien:_Earth is the next best thing, as it starts off about 2 years before what happened in the 1979 movie.
