How do I post youtube video to weibo.com?

The short answer is you cannot.

The long answer is you can, but only a link and I have found that posting links, even for a new account will generate some traffic.  The site viewership is huge and even a small percentage of click throughs has an impact.  Weibo Sina is starting to convert some of the site to multi-lingual.  No I don't count 3 versions of Chinese as multilingual.

...bottom line.  Use Chrome simply because built-in Google translate is faster to use than Bing translate.  It's still incredibly tedious though.

Good luck.  If Weibo's policies on imbedding youtube videos change I will update this post.