Next go inside the WTF folder and go inside the Account folder. Once done with that go back into your WoW Retail Folder and delete the WTF and Interface folders and then take all the folders from the SyiUI zip and paste them into where you just deleted the WTF and interface folder in the WoW Folder. Locate your WoW Retail Folder and make a backup of your WTF Folder and Interface by copy and pasting them somewhere else outside of your WoW folder, this is useful to have if you want to pull old addons from your old UI or just completely go back to it.
