Just wait some time, it will update automatically, but if you  want to, click your profile name -> my database -> click on the gear icon beside your database -> upgraded

Hi,

If you're using Odoo Online (odoo.com), you don't need to manually upgrade from 18.2 to 18.3. Odoo handles minor updates like this automatically. Your system will be updated in the background during a scheduled maintenance window.

You can check your version in Settings > About. If you're on Odoo.sh or on-premise, the upgrade requires pulling the latest code and restarting the server manually.

Hope it helps.