Better description, please?
But....if they accessed and put a password on the system...you personally need to do several things.
1. Disconnect that system from any and all internet access. Do this now.
2. From a known good system, change ALL of your usernames and passwords. All of them.
3. Consider calling your bank and changing all credit card numbers.
4. Do a full wipe and reinstall of this system they had access to. All of it. No questions, no excuses.