canonicalisation issues (I can't even spell it!)

I think I have a canonical issue going on on my site, and I want to try and fix it. But I'm a bit confused...

I've been doing a bit of research on it, and I think I need to install a .htaccess file. I have no idea how to do this...

Though, perhaps I can just use 301 redirect? I don't know how to do this either though...

So I was wondering if anyone can advise which is easier, or better to do... and how I do it...

Or, is there a wordpress plugin that can do it for me?

Any info is appreciated, thanks.

.htaccess is simple file, you just need to upload it to your server... it got few lines of codes and if you need you can add more...

There is nothing to install, usually you can find it in your hosting... Talk to your hosting provider and they may do it for you...

You think you have a problem? Why and what exactly is the issue? www vs non www? Before you start trying to fix things you really should know exactly what the issue is.