If Loki is trying to conquer he's more than likely going to simply go after/replace Hippolyta using disguises and spells. I don't think he's likely to openly engage the entire Amazon military singlehandedly like Thor would try to do. He'd disguise himself as an Amazon, get access to Hippolyta, and cast a spell to put her in suspended animation for an extended period of time, then replace her and command the Amazons for a time until Wonder Woman figured out he wasn't her mother.