The error means that Odoo is trying to connect to PostgreSQL on localhost:5432, but it's not providing a valid password. This could be due to several reasons, especially after reinstalling Odoo and PostgreSQL or after installing a newer compilation of the same version 18, since the odoo.conf is overwritten in the process (You should back up that file before reinstalling).

• Check if the PostgreSQL service is active.
• Check Odoo's configuration file and look for: db_password = your_password (C:\Program Files\Odoo\Enterprise\Odoo 18<some_version>\server\odoo.conf)
• Check if the odoo user has access to PostgreSQL.

If this is too technical and this db is new, I wodul suggest uninstalling, rebooting and reinstalling, being very carefull to take note of every credentials your configure.

You're setting up Odoo on a laptop which suggest you're studying it. Installation is the first chapter in all Odoo's book or documentation. Just follow strickly any documentation, how how to setup odoo 18 for your OS. 

In your case: pay attention to the part where you create a user for Odoo, (Odoo doesn't accept postgres as a user), set a password to that postgres users, (possibly have to configure pg_hba to support login with username/password), specify the username/password in the conf file.