with the motor cold, take off the radiator cap. then turn the motor on. let the motor idle unitl it warms up. the whole time its warms up it will purge bubbles and want to overflow out of the radiator. I usually tap the top of the radiator with my hand and squeeze the upper hose to help get the bubbles out.
it will leak no matter what (hence the papertowels)
when your motor reaches temp the Thermostat will open and you will notice the level drop in the radiator. top it off and let it flow for a couple minutes. it may still have a bubble here and there. once its flowining well put the cap back on.
another trick i do is drill a 1/8 inch hole on the upper section of the t stat to let the bubbles through if any.