Please try by using small featured image, which will align featured image on left with content on right of blog post . For this
GO to dashsboard->basic setting-> Featured Image->Checked small featured image
To place featured image on single post you need to do customize content-single.php templates.
Note: If you are not technically sound on WordPress you need to take help from developer, As you need to to make some change on Html structure and coding too.
I think I didn’t explain exactly what I was talking about…I am referring to the featured image left of text NOT on top of the text in a post? Sorry for the mix up:)