The anchor light is all around (360 Deg) white. The steaming light is a white, forward only (135 Deg), not all around.
The four wires going to your mast are: ground, steaming light, anchor light and deck light. Buy or borrow a multimeter and use it to determine which wires are ground, steaming, etc.
Since you currently only have two wires in your mast, you can only wire one of the above. I suggest you wire up the steaming light. When motoring after dark, you are required to light it. It's switched off if your under sail, not motoring. When anchored, you need to show an all around white light. If your planning to anchor at night, you'll need to either run additional wires up the mast (and maybe add an anchor light to the masthead?) or buy a "portable" anchor light.
For the long term, you'll probably want to rewire your mast.