Q: how can i copy files from pc to ipad

You first need an app on the iPad that supports the type of file that you want to copy to it - the iPad doesn't have a file system like a 'normal' computer, everything has to be associated with an app. As to how you then get the file to your chosen app will depend upon what the app supports - different apps will have different ways of copying their content to/from a computer e.g. via file sharing section at the bottom of the device's Apps tab when connected to your computer's iTunes, via your wifi network, email, dropbox etc.

What kind of files are you trying to copy?  Music, pictures, documents, PDF?