Originally posted by Focalpro:

1. What are those dark circles around attack points on map?

The control point circumferences? Killing planes inside that area help with the capture. Killing planes outside of it will not.

2. Point isn't full blue, what do I do to make it better?

Plane kills contribute to the cap total, both enemy and neutral air-defence. Friendly plane deaths detract from it.
Destroying ground targets contributes to capturing, with different structures having different values[wiki.wargaming.net]. Optimising your strikes so you're bombing the maximum number of high-value targets in a pass is valuable.
Ground targets will respawn, so you can just wait to make another pass in a bomber / ground attack craft.

To defend an area, you've got to kill planes that are trying to contest it. Bombers can't really do that particularly effectively, and if you get blown up in a perimeter you'll count towards the enemy flipping the zone.

If the zone is "padlocked" (shortly after being capped), then neither team can do anything to effect its cap status until the padlock goes (usually when the enemy air defence bots spawn).

As a bomber, you have a few options - your supplementary cap points from destroying ground targets might be enough to flip a control point. And a flipped control point can mean respawning AA and air defence bots to help teammates who are still active over that point.

But a particularly high value thing to do is go to installation types that have particularly few air defence fighters and / or particularly hardened ground structures and solo-flip it (although a ground attack craft clearing out AA guns for you can make that way way easier). Friendly lights, heavies, and multiroles tend to want to be shooting down air defence bots and enemy team planes to flip a CP, so will want to be contesting those CPs rather than something like a factory.

Aside from that, prioritise high-value sectors first. So Rocket bases > Bomber command satellite dishes > Factories > Airfields > Garisons.

good game