Add/upload a video to a post (not embedded videos)

Hi

I want to add an uploaded video (not embedded video from youtube) to a post. I want the video be in the middle of the post or page and see the thumbnail and then click to start the video.

I have the videos in the Media-> library but at the moment the post have only a link to the video. I want to create a blog post with the video in.

I have created the videos in the HD size 1280 x 720 and they seem to be very big. Can I resize them in the HTML-mode when editing the post?
But first how to get them to the post?

Thankful for help.