Hello there and welcome to the forums
The best board for newbie questions is this one
http://aurora2.pentarch.org/index.php?board=19.0so the thread will most likely be moved
Regarding your questions:
You start with a small stock of maintenance supplies on your planet, and your engineering sections are already built up "topped up". So when a new ship launches, you do not need to fill it with maintenance supplies, it's already filled. But...
These supplies are used when components break, or when combat damage is to be repaired. For civilian ships, this does not happen unless the ship gets damaged in fight.
For military ships (not only warship, even just gravitational survey vessels do qualify), you will see that while they operate their maintenance clock goes up. As it grows, and depending the maintenance life of the ship (more engineering sections = more life), components will start to break. If there are enough supplies on the ship (say, fifty for an engine. Depends really), then the component will be repaired and the supply points used. If not, the component stays broken.
As I said, points will also be used after or during a combat to repair damaged parts. For repairs during combat though, you will want the specialized damage control component. Anyway, a fleet in heavy combat can use a lot of supplies, especially afterwards to repair damage, so many players have "supply ships" which carry additional maintenance supplies through the Maintenance Storage Bays components. Or you can have your supply ship in a close enough place so it can be moved AFTER combat to join the fleet.
To refill your ship of maintenance supplies, you give a task force the "resupply" command. For example, "Resupply at Earth", and if there are enough maintenance supplies, the ship will resupply.
A not so obvious tip is: when you see that a ship maintenance clock is coming close to its "Maintenance Life" as shown in the ship design, it's wise if possible to overhaul it. This slowly brings the clock down until it reaches 0, but the ship is unavailable while this happens. Consider it downtime , while your tech guys do maintenance and restore the ship in pristine conditions.
A practical example: your gravitational survey ship has been out there 2 years (as shown in the maintenance clock). It had one engine breaking down, though it was repaired, so supplies are down by 50. You want to restore it to top condition.
You select the task force (grav survey vessels are usually in a single ship taskforce), select Earth and add the following commands: refuel at Earth (good practice whenever you return home), resupply at Earth (takes no time, will restore the 50 missing supplies taking them from Earth's stock), and finally Begin overhaul (which will bring maintenance clock down to 0 in about 8 months in this case).
More info here
http://aurorawiki.pentarch.org/index.php?title=Ship_MaintenanceAs to how many supplies you need, you'll get a hang soon enough. The more military ships you operate and the more combat you have, the more supplies you need. In the beginning, if you are in a peaceful situation, not much. Later on.....
