How to correctly specify the versionCatalogs in the settings.gradle.rts file

Here is my settings file

pluginManagement {
    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}
dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
    }
    versionCatalogs {
        create("libs") {
            from(files("libs.versions.toml"))
        }
    }
}

rootProject.name = "PersonalFinance"
include(":app")

I get the output when synchronizing

Invalid catalog definition:
  - Problem: In version catalog libs, you can only call the 'from' method a single time.

I don’t understand where the system sees the duplication from. how can I resolve this error? or at least see where from is duplicated

That’s an unlucky message unfortunately.
The problem is, that what you try to configure is the conventional default.
And that is then recognized as “two from calls”.
Just remove the whole versionCatalogs block and you have the result you want.
This is the issue you are hitting: Unclear error message when reimporting the default version catalog file · Issue #21328 · gradle/gradle · GitHub

tell me which file gradle libs is linked to by default

Ah, wait, I mis-looked, it is not the default config you try to do.
The default is exactly where you have it or you wouldn’t get the error message.
The default is gradle/libs.versions.toml.
If that file exists, a libs version catalog is created or if already present configured and the from call with the file is done.
If the file does not exist, then not.
So you have the file gradle/libs.versions.toml but try to configure libs.versions.toml which then fails due to calling from twice, once explicitly, once implicitly.

You can use the default file gradle/libs.versions.toml that already is present and remove your config.
You can remove that file and use a different location and configure it like you have it.
You can have both, but then use something different than libs for your additional version catalog.