I'm using pgadmin 4.21 on postreSQL 12 on a macbook pro running macOS 10.12.6.
I ran it by right clicking on the table I wanted to fill and selecting import/export to run the wizard.
For future reference pgAdmin is created by a third-party that provides their own support channels [1]. This mailing list, pgsql_admin, is not for questions concerning their product but rather questions pertaining to the general administration of the PostgreSQL server (even though in practice this list should be discontinued as it gets more mis-postings about pgAdmin than it does on-topic postings...). This topic is off-topic for this list.