You may want to add a border for your Text Tile and to do so, you need to set the border values for your Style Preset in the Theme Editor.
For more information on how to create a Style Preset, please click on this link.
To create a border for your text tile
1. Search for your theme and log in to Theme Editor.
2. Go to your Style Preset > Tiles > Border
3. Here you need to specify the value of the Border
4. Follow the syntax below when setting the value for Border:
<size> <style> <#hex>
1px solid #000
5. Click on Done, then Publish the theme.
6. Apply the Style Preset to your text tile in the Site Editor.
**If the site/site editor was already open when changes to the theme were made, you will need to refresh the site/site editor for the changes to take effect.