Adding Custom Meta Boxes

Hey guys,

I’m having trouble with adding a meta box to my “add new posts” pages in the Admin area. My theme original came with an option to add a video using a meta box from the a custom ‘reviews’ page type but i’d like the option to add them to posts as well. Here’s the code I cooked up:

Pastebin: https://pastebin.com/embed_iframe.php?i=xCiddYne

I’ve been working on themes for about a year now but this is my first time experimenting with adding changes to the Admin panel, so any help you guys could provide would be much appreciated. Sorry for the no link, link. Windows 8 isn’t behaving today.