Indeed, drop some terraformers on there or put some ships with terraforming modules on there and start pumping out safe greenhouse gas from the environment summary window, one of the tabs where you find the shipyard menu, summary window etc. etc.
Be warned, ground-based terraformers need a population of 250,000 to run I believe it was. It will take a long time or lots of terraformers to make it livable, though.
EDIT: That won't change the base temperature because it can't be changed, it will change the surface temperature and make it livable, though.