Complex sentence: Instead, they decided to capitalize on its location within the Square and market the tower as a location for billboard advertising; the entire exterior of One Times Square above the ticker was modified to add a grid frame for mounting advertisements.
Split into simpler sentences: Instead, they decided to market the tower as a location for billboard advertising, capitalizing on its prominent location within the Square. As such, the entire exterior of One Times Square above the ticker was modified to add a grid frame for mounting advertisements.