The simple answer is that I don't know how to yet. I'm sure I could work it out but it's not as easy as doing something like a paypal purchase. You have to set up a coin account, buy bitcoin, then buy steem, then power up. At least that's my understanding.
I think you're right on Steem though, it will go up in the longer term but not before a significant correction that will occur in sympathy with a bitcoin crash. Steem is one of the crypto's with utility other than just pure currency so I see it doing well in the long term.