Your question should be "how do I search, so I can find out how to do these things?"
I will help you. At the top of the screen push the little magnifying glass beside the "Submit a story link"
Type in something. For instance, you said "how do I post videos"
I typed in the search:
how to post videos
and a WHOLE TON of links with explanations showed up on how to post a video on steemit.