In the admin section of WordPress navigate to a “Post” with a “Gallery”.
There are 2 ways to access your uploaded images.
In the overlay dialog box click “show” next to an image.
Add title, media, size and date to “Title”.
(As you get to know WordPress, you may want to use the other options. For now, leave them as is.)
Repeat this process with all your images.
Once you have finished click “Save All Changes”, at the bottom of the list of images.
Because this is a “Gallery”, do not click “Insert into Post”
Exit the dialog box by clicking the “x” in the upper right hand corner.
Be sure to click “Update” in the right hand corner of the Edit Posts page to make sure you have saved the changes to the page.