Complex sentence: In August 2015, the cover of the September issue of "Vogue" magazine was unveiled online, with Beyoncé as the cover star, Beyoncé becoming the first black artist and third black woman in general to cover the September issue.
Split into simpler sentences: In August 2015, the cover of the September issue of "Vogue" magazine was posted online, with Beyoncé as the cover star. This resulted in Beyoncé being the first black artist and third black woman in general to cover the September issue.