Update PG Admin

Uninstall Existing Instance(s)

1. Open "Add or remove programs"
2. Search for Postgres
3. For each version installed:
   1. Click to uninstall the application
   2. Accept the Admin changes popup
   3. When the PostgreSQL Setup application appears, you will notice two radio buttons. Select the second one to uninstall only "individual components"
   4. Choose to uninstall PG Admin and continue

Instructions found on Stack Overflow

Install the latest version

Get the latest version from the Official Website