Nostalrius Begins - Quality wow vanilla realm (1.12)

Hello,
I log onto my account yesterday 3/21/2016 and discovered approximately 10 gold was gone. My character's name is Dungadin. My two alts are Artio and Lanceboyle. It happened on Dungadin. I am not so much worried about the gold being gone as I am concerned about somebody getting into my account. I was saving for my mount. I would change my password but am not sure how to do it. Thanks for any help!

to change PW:

https://en.nostalrius.org/password

Thank you so much. I have changed my password.