If you are a verified creator and have access to prefixes choose the prefix for your series from the prefix dropdown. (If your series doesn't appear, leave your series details in the Prefix request thread found in creators forum and I will get it added ASAP)
In the thread title just enter your Video title, I would advise just copying it from the Youtube Video itself.
In the body of the thread first post the URL to the video. When posted the forum will take this URL and automatically embed the video
Then under it write a description of the video. Again you can just copy it from your Youtube video or create a bespoke description