Installing 3 way Dimmer on Single Pole

Hi all,
I've searched but can't seem to find a simple answer. I'm swaping out a simple light switch with a 3 way Lutron dimmer. The problem is that there are just 2 black wires coming out of the wall switch box. The dimmer has black, red, red and white and green (4 wires).

I know the green is ground and that the red and white gets capped because this is not a 3 way install.

The question is which black wire goes to the black and which goes to the red??? There is nothing indicating any difference. Also the old switch was not grounded. Must new one be grounded?
Thanks in advance.

 

On a single pole it does not matter which is hot. Check the wiring diagram on the dimmer to ensure the correct connections are made. Normal dimmers do not need a neutral connection.

Is there a ground in the box?

 

Thank you. Are you saying it doesn't matter which black wire from the wall goes to black or red wire from the switch?
Inside the box, there are several bare ground wires connected with a cap. Also several white wires connected with a cap. I'm assuming the bare wire is ground, but I didn't want to mess with it.

 

Yes, it always will be.On a non 3-way circuit that is correct.

 

and I should definitely connect the ground wire to the bare wire in the box, right?

 

Yes the grounds all need to connect.