At the top right hand corner, you will see three lines. Click on them and then click on FAQ
Here is a clause from it that may be of use:
What should I do if I discover that someone hacked my account?
If you made your account through Steemit and it is compromised, immediately visit the Stolen Account Recovery page. This link is also available in the main site menu. You will need to provide the email address that you used when you signed up, your account name, and a master password that was used in the last 30 days.
Link for Stolen Account Recovery:
https://steemit.com/recover_account_step_1
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Good luck - and keep in mind that you should only use Steemit while logged in with your posting key. It makes it more difficult for hackers to get your active key.
EDIT: I returned to mention something important. NEVER ask others, in your comments, to vote for you, or view your posts or to follow you in return. Just say something like, "I loved this post, so I am following you.
Asking is considered bad manners and SPAM, which means you will get flagged. Also, do not use one reply as a comment, people can go to your Home page and see what your other comments are like, If they are similar, not personal for each post, then you will get flagged.