Open this link and download the latest version of postgres.

Click the downloaded file and install it. Keep everything default and click next.

It will ask for a password. Enter the password and click on next.

Go to C drive and go to Program Files and open the PostgreSQL folder. Go to the bin folder. Copy the path of the bin folder.

In the search bar type env. You will see
Edit the system environment variables. Click on it.

In the system properties, click on the environment variables.

Click on the Path and click on Edit.

Click on the New button and paste the path of the bin folder. Click on ok.

Now you can use Postgres in the SQL terminal. For this in the search bar type SQL. It will show you a name called "SQL Shell (psql)". Click on it.

You can also use the command prompt to use Postgres. For this in the search bar type cmd. It will show you a name called "Command Prompt". Click on it.

Type psql -U postgres. It will ask for password. Enter the password and click on enter.

Now you can create a database and use it.