Similar to Medusa V, you fight battles, take pics, write up a BATREP and submit it to the guy running it, who complies all the reports per week and spits out updates as to the status of things based on those BATREPs. The FAQ covers most of the basics to it, and the template for reporting is in the Report a Battle link. There's no minimum of BATREPs that need be submitted, and no requirement to register.

The basic premise is fairly simple: the AdMech accidentally awakened a Necron Death Star, and had to call in heavy reinforcements to prevent it from fully awakening. Now the thing is slowly drifting towards a star, but the Necrons are trying to repair it before it burns up.