Oh, that's a easy one. You need to download the RPGVXAce Runtime.
Here's the Link: https://www.rpgmakerweb.com/download/additional/run-time-packages select "RPG MAKER VX ACE" then click download now.
then just extract the archive you just downloaded and execute the installer.
If something isn't working, just reply, I like to help People (･ω･)