Personally, I prefer to do it in my PC or laptop. Connect the phone by USB and put the SdCard into a carrier that can fit a computer then use Windows file explorer to cut and paste. Before cutting, make sure the file isn't crucial to Android's running. Some files have to remain in the internal system.
If you prefer to do it in the device, the File Manager should offer you the option of copy or move when you press the filename or folder name then switch to SdCard and select Paste but things have been known to go wrong that way. It's safer done on a PC.