The basic process is :
Step 1: Convert your money into Bitcoin.
Step 2: Use your Bitcoins to buy Steem!
More detailed steps below:
1.Firstly you will have to signup for a website that allows you to buy Bitcoins. I suggest https://www.coinbase.com/join/5aa4fc1aaf0f8203a8875ad4, because it is popular and safe.
2.login and purchase Bitcoins using the site's "Trade/Buy" interface. You can enter the amount in USD or in BTC which you prefer.
3.After purchasing Bitcoins, login to Steemit.com, and open your wallet. Your wallet can be found by clicking on the "Wallet" link under your 'profile' picture icon. (It is in the upper right corner of the Steemit website.)
4.Inside your wallet, click on the drop-down next to "STEEM", and click the "Deposit" link.
5.Decide if you want to purchase "Steem" or "Steem Power".
6.The popup screen will have a "Wallet Address" near the bottom. This is where you will need to send the Bitcoins to purchase. The wallet address is the long series of letters and numbers, which is right after where it says "Send Bitcoin To". Copy this address to the clipboard. It is important that you copy the entire address, exactly as it is shown, without missing any of the letters.
7.Go back to the site you used to purchase the Bitcoins, and find the place where it lets you send Bitcoins. Enter in the wallet address that you copied from Steemit in the previous step. Enter the amount of Bitcoins you would like to send, and click the "Send" button to send them to your Steemit account. It will likely ask you to confirm. After that, you should see a success message showing the transaction was completed!
8.You will need to wait a little while for the Bitcoin transaction to confirm on the network. Most sites like Coinbase will show you the status of the transaction. Periodically check back and refresh. Once the transaction is confirmed, it will show up in your Steemit.com wallet!
Then it is done!!!
Thanks for reading this guide.