how to get www infront of site name

When you go to my site, the address looks like this: https://kpbranddesign.com

If you type https://www.kpbranddesign.com it will still take you to the site, but does not display the www.

I really would like this to have www. in the address. I have read the documentation on this here: https://codex.www.ads-software.com/Giving_WordPress_Its_Own_Directory

When I tried what the article said it did not work for me, & I was not able to access my site. I had to uninstall & reinstall wordpress.

If anyone has any suggestions I would greatly appreciate it. Thanks!