https://steemit.com/steem/@steempower/how-to-buy-steem-directly-within-steemit-com-powered-by-blocktrades

Here you go, full detailed tutorial.
And I won't recommend to invest much money, if you are new to crypto currencies,
Unless you are a blogger with good content and you know " STEEMIT IS YOUR TYPE OF THING ".

GOOD LUCK :)