Welcome to the Orchid Board, ghostlupo! You can and will become an old hat pro with these plants. There is a lot of information and helpful people here.
Mold on orchids usually grows only on dead plant parts, so you just need to remove the dead parts. The problem is, why are there dead parts? Most of the time it's overwatering, and roots staying too wet. When the roots die, the leaves start to turn yellow, because there aren't enough roots to supply water.
I'm not sure which plant you mean. If it's a Phalaenopsis, there is a lot of information for newbies here (I'm a phal newbie, I've killed lots of them.) Go to these threads in the Beginner Discussion and read the first few pages in each:
The Phal abuse ends here.
Using skewers to determine when to water
Ask if you still have questions, but we would need more information from you. What plant is it? What is it potted in? What kind of light, humidity and temperature is it getting? How are you watering it?