This is a single-player event (not the entire alliance). You should join because there are few risks and a lot of rewards. Like most events of this type, it goes crazy fast. You won’t lose troops, so it’s worth trying because there’s rewards for every level. Here’s some tips on YouTube. This is a really great guide as well for maximum ore procurement.

The goal is to get as much of the ore as possible as quickly as possible.

Before you start: Heal all your troops and recall them all.
There are three minutes at the beginning before the action starts, so feel free to read and go through the tutorial. Then pick a spot between level 2 and level 3 mines towards the center of the map, unless you are low level. Try to find a spot away from as many players as possible (it’s hard). You want short troop marches.

There are four things you can do in this event (one is a special one at the end).

Killing NPC troops = buffs.
Mines = ore.
Vein explosion = LOTS MORE ORE.
Attack other people’s mines = points
Smelter=King of the Hill at the end. Unless you’re very strong, ignore this one and focus on either gathering or mine patrols.

Keep your troops working the entire time. You can attack other occupied mines (others will attack you). Ideally you want to aim for trying to get 150,000 ore the fastest way possible.