Yes, that screw needs to come out. You've got the grounds and neutrals nicely landed on their respective terminals, but they're interconnected by the screw if you don't remove it.

Note there is one on both sides of that panel. You'll also need to bridge the two neutral bars to each other (this is why they give you the extra larger terminals).

I do not see a screw (green) one on the neutral side (bus). I only see the screw that holds the bus with those lugs? Am I not seeing it?

The second pic - shows the ground bus side. See how there are two screws? I see what you are saying about pulling the one green screw out. However, the second screw seems to hold that bus to the lug. The same goes on the neutral side - but without the bond screw (that I can see).

Is there not another green one on the left hand "neutral" bar, just under the two large terminals at the top?

No. Just one screw holding that bar to the black

Get rid of the green bonding screw if you're feeding this as a sub panel.Your ground from the incoming supply cable will now be going on your ground bar. The neutral bars come from the factory connected on both sides.You're good to go when you put in supply!