Put the downloaded SVG file in the same folder as the .SCAD file
Type the filename into the customizer
Select the Custom Logo Option
You may need to change the file scale setting
Notes
If you want to print a double sided tag, you can set Base Height to 0 and export the second side. Then just flip this over in the slicer
If you want a different color for the logo and code, you can enable Custom Logo and leave the Custom Logo File field empty. Then to get the logo, use text and just enter a space.
You can rotate the Heart Hole keyring option using the custom logo rotation settings
If you want to rotate or invert the Spotify logo, use custom logo and one of these