need an app to launch Sims 4

I recently just purchased Sims 4 on my Mac. I have it saved on origin, but every time I click the download button I get a window that pops up and tells me I need to use an application to open the game. I also tried looking at the app store to see what they wanted me to use, but nothing shows up. If someone would be able to help me that would be very much appreciated!