Hi Katie. First let me also welcome you to Mobileread! I think Alex tried to find the answer to your problem in the second part of his reply. You can use the built-in "File Explorer" to move files that are in the RAM of your handheld to the memory of your SD Card (I assume you have the SD Card inserted in your handheld, as you mentioned in your first post). Let me try to help you some more (I attached a few screenshot I just made for you ):
When you start File Explorer, you first see the content of "My Device". This includes one folder called "SD Card" which holds the content of your inserted SD Card (Screen001).
Let's say I want to copy a file called Note1 stored on my handheld in "My Documents" to the root directory of the inserted SD Card. To do so, I first browse into "My Documents" (Screen002). Then I go to the file Note1 and click on it (I must hold my stylus on it for a second so that a context menu can appear). I then choose "Copy" (Screen003). Now I go back to the root directory of my handheld "My Device" and browse into the folder "SD Card" to actually access my SD Card (Screen004). I go to the directory on my SD Card where I want to copy the file to. In this case, I will choose the root directory. I then click on Edit and Paste (Screen005). The file Note1 from my handheld is now on the SD Card.
Hope these steps are easy to follow.