I'm experiencing Technical Difficulties

How do you put links into your blogs? I'm not even sure if that's what you call them...

Example:

I posted about this last month, and it's coming back to me again.

What I want is for the word "this" to be a link to to an older post, a picture, or a website, etc.

Can someone explain to me how to do that?

(In your explanation, remember that I am mentally deficient when it comes to these sorts of things. Which is sad, yes, but true.)