I see a lot of pages engaging their user using funny pictures with captions. Does anyone know where they find these?
That's a very vague question but I assume you mean memes. Particularly those built with http://memegenerator.net/
Exactly. I have seen pages with videos with a caption and a short story. See example:
https://www.facebook.com/WomanFreebies/
I wonder if I need to hire a writer to find videos and write something it or if there is a service where I can pick these up and have someone add them on the fb page.
To do well with these you really need to have your finger on the pulse of contemporary trends, viral stories and memes.
You could hire a "social media manager" i.e. a stay-at-home mum who spends 4 hours on the internet each day and clicks/likes/shares every video she watches.