For edit your text in OS Joomla Slider
1. Login to website frontend as site super admin
2. Go to frontend, where you see your slider
3. Click on joomla slider "edit button"
4. On Tab "Images", on the image where located your text, Click on "Pencil" image, You will go to list of all your "text"(HTML) objects located on this image
5. There you may or ADD new Text(HTML) or edit text which already added.
For edit - Click on Pencil with your Text Object.
After that - you may as edit this text, and edit it settings.
- for move text - you need click on it and with help Mouse, move to position which you need
- Together with text - you may use any HTML code, with links, images...
More details in Joonla Slider documentation