If you are refering to apps, then launch "Settings" and go to "Applications" then "Application Manager". The exact labels may differ from device to device, so know what device you have would be beneficial in giving you most specific guidance, here. Once you've got the Application Manager open, tap an app you no longer want, and press the "Uninstall" button.
If you are refering to files you have downloaded, then it works pretty much just like a Windows desktop. Launch the file explorer of your choice and then navigate to the directory where the file is. At this point, the exact method can vary slightly. Personally, I prefer FX File Explorer, but for most it's just a long press on the file, then select "Delete" from the popup menu.
https://forums.androidcentral.com/e...ore/apps/details?id=nextapp.fx&token=jI0OOvAP
FX File Explorer is free, with a paid version available for $1.99