If your story looks like this when you publish it:
And then, behind her, stood a cloaked figure. It had no visible face, and seemed semi-transparent even in the darkness.
Then it's quite easy to fix. All you have to do is not indent your sentences. I know that it's kind of hard, but wikia doesn't support indentions of any kind. Instead, try to double space your paragraphs (pressing enter twice). It makes it to where your paragraphs are spaced out.
There is a way to leave indentions in your paragraphs using source editor. This uses the <nowiki> </nowiki> text which does not convert the indentions to wikitext.
Using visual editor is ill-advised while copy-pasting from MS word, etc. because it leaves formatting errors behind when viewed in source mode.