please note I don't have this phone so this is a generic answer.
If you click on settings Apps-SD Card you will see what is on the sd card and you need only highlight the app, file etc. and select remove or uninstall. That is one way. Now to the next method.
on your phone you have a picture gallery, a music folder which you can simply just hold down on the song and choose delete, same applies to pictures you no longer want. Long press and then select delete.
Another way is to go to the Google Play store and get the Astro File app. this way you can see all the files and folders on your phoes internal memory and sd card. there is an option to delete files and folders from the Astro App.
Another way is if you have a removable sd card and have a adapter to be able to place into your computer, you can then delete files etc. that way.
Be careful deleting any file, folder, or program. it may cause you huge problems .
Fantastic question! To erase your entire SD Card, you can re-format the SD Card. Please follow the directions listed in the link http://vz.to/11OJ8fm. Keep in mind, once you re-format the SD Card, any information on the card is deleted permanently. Hope this helps!