Adding line and space between posts

I would like to add a 2px line and some additional space between my posts. All my posts look like they’re running together with the current spacing.

I’ve seen repliesto similar questions, but I don’t seem to have the code that they refer to so I’m not sure what to change. URL is
http://luvemorleavem.com/relationshipvideos/

Thank you!