Hello @perelin!
Since you are self hosted, you will either need to query the Postgres DB that holds the user data for your instance. This information will not be on Retool DB as you are self-hosted 
First you will need to get the credentials for the database.
These credentials would have been set when you were first deploying retool to wherever you are hosting the servers.
Once you have these credentials, you can add this Postgres DB as a Resource to your Retool app.
From there, you will want to query the 'users' table. This may have a slightly different name depending on how you had this set up during deployment.
Once you have found the right table and queried it, then you can specify what information you need from the table holder users data (name/email, etc.).