Yes, you can add text, drawings, or other simple shapes (lines, rectangles, and circles) to your image(s). First, choose a frame on which to draw. Then click the "Edit Frame" button to the left of the playhead controls. (You can also double click on the frame you want to edit). A screen with paint toolbox menu on the left side will appear. Select the icon of your choice and begin editing your frame!
When you are finished editing, press the Done button (bottom right) to return to the main screen, and your edits will appear on the previously selected frame.
Note: Clicking the Undo button will remove the edits you made, and clicking Revert will clear all edits made on that image.