You probably misunderstood and the game is telling you to download Origin (not an app) which is something similiar to steam, it just hosts EA titles and is a lot, lot worse than steam. However, if you bought a physical copy the game will usually prompt you to log into origin during installation. You'll need to register a free account to register the serial key etc. After that you should be able to play the game offline from origin.
Origin
https://www.origin.com/store/downloadHowever, if the game after installation still wants you to use origin you can do a couple of things
1. In the settings of the game untick the online options from the community tab
2. In the root installation location, find a file called TS3W.exe. Right click it and choose to make a shortcut to desktop. Launch the game using that shortcut. This'll bypass the launcher, which usually helps with any third party programs trying to force you to log in before playing.