fd.vintagealice on "Space between paragraphs"

Hi

I have written a new post and when I hit return twice, to create a new paragraph, the space between the paragraphs is too big.

I have searched the forums and found responses on this topic, but as a complete beginner to Wordpress, I'm afraid they don't make much sense to me.

Can someone explain, in an idiot guide format, how I go about changing this?

Thanks