I will try to answer your questions but you may want to research further as there are articles with more information.

• To post your own video, you can do so through @dtube or @dlive platform that are link to steemit actually.
• Delegate steempower is like borrowing steempower from others. If you look at your wallet, you will see there are some steempower with a bracket that is delegated to new members. Some members are able to get free delegation of steempower through their networking or contest for minnow while others may just buy them.
  It is always better to buy steempower rather than rent them as it is not really yours. Delegated steempower is not yours actually but you are borrowing it.
  As new member without much cash for investing, it is always common to post and accumulate the steempower slowly. Find articles and read more about it as there may be more details that I cannot explan clearly.