You just go to the currency exchange here... its much easier... Its in the menu tab on the top right of the site
Click on currency exchange and you want to "buy steem"... pick your conversion rate.. They have moved the conversion rate a lot in the last week... I was getting it at .36 and .37 and now its in the .50s range. I'm not sure how the fluctuations are, but that is a very big move in a week.
I would suggest that you go to @bumper and use their service... I'm doing it now for my sbd's... I'm still in a test phase, but so far I've had 7 tests and all have outperformed their promises... If you would like to know more about how it works just let me know.. Like I said I'm in the trial phase so not ready to broadcast loudly but I have 21 tests in progress now.
I'm going to sleep right now, but if you have any questions I'll be happy to answer in my morning @marinaart :)