I have a dimming wall switch to put in.

[APBurner]

I have a dimming wall switch to put in. But I opened up the box and only have 2 wires into the box. What do I do.

[BLH]

Both wires are connected to the original wall switch? You have a switch loop with a Line and Load connection.
You could use the 2474 Two Wire Insteon wall switch. That limits you to only using incandescent type bulbs.
You maybe able to rewire the switch loop. To get a Line and Neutral wire into the electrical box. To power the dimmer with its load caped off. Then add a micro module inside the fixture to control the lights. By linking the micro module to the switch in the dimmer switch's electrical box.

[stusviews]

The standard (low cost) solution is the use the 2-wire switch. But then you're forever limited to incandescent bulbs, as BLH pointed out. The preferred solution is to change some connections in the ceiling box and Install a Mincro Module (in the ceiling box).