Export movie isn't looping

You can either write text in the normal text element, or in the 'inner HTML' view that is exposed after clicking the pencil. This might be helpful for you: Working with Plain Text

One shortcut that might be helpful is if you select the text element in the element list, and then press on the keyboard ⌘ + option + e

This will pop open the text editor without you needing to adjust the element's layer order.