Here is the install sheet for this unit. It has wiring info.

Looks like you are part way through the install.
Are you sure that the wire you have attached to the unit's case is Neutral?
Looks like the ground strap is installed (center terminal strip to machine frame). Did you do this?
All the connectors on the line coed look discolored. I would clean them up with some fine sand paper or emery cloth to be sure that you get a good connection.
The line cord wire you have attached to the case should not go there. It should be attached to the machine frame (the lower ground strap screw).
The reason is that the case connection may not be good enough to carry the heavy current load and may overheat.
Then another wire from the case should go to this connection point (ground strap), you will have to add this.
The 2 loose white wires also have to be attached to the ground strap screw.

[COLOR="Blue"] Does this get attached to the middle?[/COLOR]
I am no 100% sure as I am not there. The middle wire should be the ground/Neutral connector at the plug.

[COLOR="Blue"]Is this where the white wires go?[/COLOR]
Yes, I think.
Perhaps a bit of an explanation would help you.

On a 4 wire system you have L1 (black) (one side of the line power 120volts), L2 (red) (the other side of the line 120 volts, Neutral (white) and earth ground (green).
Neutral should have been connected to the center terminal strip connection along with the white wires.

Once you have it hooked up. It would not hurt to run a load on high heat and then once it is finished, unplug the unit and see if your connection has heated up. if it has you have a bad connection and will have to redo it as it will eventually melt the wires and fail.
Earth ground gets connected to the machines frame/body.
Note : No ground strap is used.

On a 3 wire hook up the power sides are the same as 4 wire.
But there is not a separate earth ground wire so Neutral is also use as earth ground. The ground strap then connects the Neutral (center terminal) to the machines frame

[COLOR="Blue"]Does it matter that they don’t have u-shaped clips at the end?[/COLOR]
It should not. I would strip them back enough so they can loop once around the screw that is attached to the bare metal plate in your photo. Then connect then clip from the line cord goes on last.
This ensures that when you tighten down the screw you will not twist the white wires.

From your picture it looks to me that the ground strap is already installed.