Option one...
1. From the main screen select "Apps".
2. Tap "My Files" and then "Device Storage".
3. "Press" and "hold" the file you want to move.
4. Now tap "Menu", then "Move" and finally "SD Card".
5. Choose the location on the card where you want to move the file and tap "Move Here".
Option two.. which personally I find way easier....
1. Connect your phone to a computer via USB cord.
2. Locate and open the folder where the items you want to move are on the phone.
3. Select all the items you want to move and either use "Cntrl+X" or click on "Edit" then "Cut" in the folders menu.
4. Now go to the "SD Card" folder and create a folder for the items you want (either by naming them individually or just naming them Music, Videos, etc.,).
5. Next enter the folder you just created and where you want to put the files.
6. When you are in the folder, either use "Cntrl+V" or click "Edit" and then "Paste" to place the files in that new folder.
7. Repeat for each group of files you are moving into specific folders.