Take him into your mouth and get him ready.... then rub the lube over his cock, while he prepares your asshole.... slowly sit down on top of him.... this way you control the speed he enters you... it will hurt like hell the first time... so sit there with him in you... and then slowly begin fucking.
before you take a real cock in the ass but a nice sized dildo and try it alone a few times,and before you take a real cock let him finger you first and get youself relaxed first
