How do you apply sign-in theme globally?

[bethany.k]

I am trying to apply a sign-in theme but struggling to find documentation on how to apply this theme type.

When I go to Tenant Environment Setup, I only see the Default Theme field, no Sign-in Theme. Is there another spot I go to apply this globally?

[matt]

Sign-in themes are for white label customers. They are used in the creation of White Label Definitions.