I would, with an army of elite orphans and sharks genetically modified to have legs and breathe on land. Giant lobsters might also make an appearance, if biologically feasible.
Once I had taken power, the world's military could be downsized and money pits that can't be used like nuclear weapons would be phased out altogether. Corporation taxes would be standardised the world over to prevent a 'race to the bottom' in the name of competition but otherwise countries would be allowed a fair bit of autonomy over their own affairs. The rights of ethnic, gender, sexual, disabled and other minorities would be constitutionally protected the world over however. Trade would be carefully managed to allow free trade whenever possible, but to also allow poorer economies to develop protected from world markets. Similarly, richer nations would be able to maintain immigration restrictions so they aren't flooded beyond breaking point.
Then? Then I sit back and get fat on my tribute as Emperor of Earth as my capable advisers run the boring parts for me ;-)