This verse explains that the reason Satan was exiled from Heaven was a rebellion or mutiny that he led in order to be able to rule over the rest of the angels.
To set himself in glory refers to putting himself above the rest of the angels, and by whose aid aspiring means that Satan was not alone in his endeavor, but rather had the help of a great number of angels who also rebelled against the order and hoped to establish a new regimen with themselves as the rulers.
The character in the part of the book can be described as careless, I did a assignment like this once and that's what I wrote and I passed but it may be different.
