How to use Yahoo Japan Buyee ? Is it a safe site to use?

I recently bidded on an seller's aution on Yahoo Japan Buyee, it is the first time I use this web. It seem like they do not allow gmail registration now because I tried register with my gmail for many times and I never receive the confirmation mail they sent, so I can only use my facebook to login. I do not know how to check my account name...but I already set my password, provided my home address information and linked to my paypal to buy things. Anybody here has experience of buying on Yahoo Japan Buyee? Here are all the options I got. How can I check my account name? Which shipping service is better and safer?
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Yoy alredy posted the exact same thread in the Q&A forum. Do not spam multiple threads with the exact same question in it