Can not change Sharing & Permissions

Hi, I downloaded an app before and want to delete it now. However, it does not allow me to delete the item, for it is locked. Then, I tried to unlock the app but found no permission. But I am already the admin account for the Mac. I have tried a lot of commands like 'sudo chflags -R nouchg /location' and so on. I would be so grateful if anyone could help me with this.