How to use alternate themes?

[x4IPx]

Hello !
In readme.md it is written that alternative themes get through Style Settings Plugin. But I do not understand how. I downloaded the plugin but did not find the opportunity to choose the topic you need.
Can you help me? Very lucky "Tangerine Dunes")

[Borber]

Activate this snippet

Set in the plugin

[x4IPx]

Thank you very much!